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A65 + A10 crank = advice requested
#826210 10/11/20 4:00 pm
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Chaps, new member here. Located in Austin, Texas.

Looking for advice on a new project.

I just bought a 'barn find' 1972 A65 for $1250. Was last registered for road use in 1981.
Wiring is completely fried. Burnt. Gone. Melted. Take your pick.. Previous owner has passed
away and I bought it from the estate sale. It's rusted to heck. Need to replace most of the
bright work, but that's not so hard.

I plan on rebuilding the engine around a large journal A10 crank and a big bore kit from E&V.
The A10 giving me an 84mm stroke and the E&V kit gives (according to the web site) an 80mm
bore, so 845cc. I am looking for advice on this aspect of the rebuild, specifically carbs, cams,
head work and gearing. I have browsed through the forums but much of the discussion about
such a conversion seems to be for high speed work. I am not looking for that..

This is going to be a rider, for the times when 'her indoors' has taken the car. I am not looking
for land speed records, but more low end and mid range. Given it's an A10 crank, an rpm limit of
6000rpm seems sensible. That said, most of the driving speeds where I live are pretty brisk. 65mph
on most of the normal roads just to keep up with traffic. 75 to 85 (yes, 85 is legal in places)
on the interstate/toll roads.

The E&V bore of 80mm seems a lot given the center head bolt. My memory of my last A65 ('69
Lightning back in 1974, left big end seized, broke the rod and poked a hole in the crankcase
while coming down the hill on the M2 from Maidstone to Strood) was that there wasn't a lot of
meat to seal the head gasket in that area.

Requested advice point 1 - I am looking for experience with that kit or direction to the SRM
kit instead.

Speaking of SRM, I plan on using their oil pump and other gubbins, but the conversion of the crank
to their end feed bearing would be pretty expensive, involving the transatlantic shipment of cases
and crank. Instead, I plan to get a custom bearing made up that's A65 on the outside and A10 on the
inside, after getting the crank crack checked and appropriately ground. I plan on using the stock rods.
In-line bore the main bush to size, indicating X-Y off the drive side main.

The engine on the bike is stamped as an August '72 A65T but it has a rev counter and a twin carb head.
Registered in the USA in February 1973.

The head is not original to the bike and has a casting number of 68-701. I am surprised at that, I would
have expected 68-704. However, the '71 and up head steady is missing and the rocker box cover matches
the head and doesn't have the 2 tapped holes for said head steady. The head has the bolt hole for the
previous head steady, but nothing on the OIF frame to bolt it too.
Anyway, let's not obsess about the head steady.

The inlet ports on the 68-701 head are as straight as an arrow and 28mm in diameter. Clearly, new valves,
springs and guides - but given my intended use - flow the 28mm ports? Can't hurt.

Requested advice point 2 - Open the ports to, say 32mm and use 2x Mk 1 32mm Concentrics from a Norton 850
Commando (with same jetting)? I tend to think that this would only help high end RPM, which isn't my goal.
The 28mm ports will keep the air flow pretty speedy and help with low to mid range, which is what I am
looking for. I understand that keeping the 28mm ports might limit top end, but that's okay. If I keep
the 28mm inlets, I would plan on using similar jetting to a 750 Bonneville, but a slightly larger main jet.
Looking for direction there.

Requested advice point 3 - Camshaft. I was going to use the stock Spitfire can. but maybe advance it a little.
I see that MegaCycle advertise cams that improve low to mid range on an A65. Has anyone experience of those
cams?

Requested advice point 4 - Gearing - My memory of my previous A65L which had 20/47 gearbox to back wheel, was
that 70mph was over 4000rpm. I want to drop that down somewhat. A 22 tooth gearbox sprocket is easy to find.
Maybe dropping one or two teeth on the back wheel? The rear wheel sprocket might be a problem as the securing
bolt heads are close to the chain. My calculator says that 22/45 give me about 3800 rpm for 70mph. Any
direction there?

Thanks for reading.. It's a long first post !

Steve.

Last edited by S-NJ-W; 10/11/20 4:50 pm.
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Re: A65 + A10 crank = advice requested
S-NJ-W #826218 10/11/20 5:57 pm
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Welcome to the forum Steve, I dont know much about the 750 conversion or A10 cranks but Allan and Gavin are regulars on this forum and have, I believe, done this conversion, so hopefully will provide more info.

Quote
coming down the hill on the M2 from Maidstone to Strood

Last time I was down that road was in 1978 on my C15 SS80 which could barely manage 65mph on the flat and on that downhill stretch it showed 70mph which probably the fastest it was ever ridden before I sold it.

Regarding the changes you plan my thoughts are as follows:-
- the end feed conversion is good but not essential as long as the plain TS bearing is line bored and crank shimed, probably more important is to use an oil filter in the return line. Consider using new conrods if you have the money, however as your bike is from 1972 you should already have the later stronger type but check for big end ovality and maybe get them polished and crack tested.
- I would be wary of opening up the ports too much, there is a consensus that the earlier small port heads perform better. I would even consider sourcing a Thunderbolt head and using a single carb which will be much easier to tune and will be smoother to ride.
- the standard Spitfire cam is generally accepted as being good enough and there's not much to be gained by going with alternatives.

Some other thoughts:-
- the oil pump you have should be the later cast iron type which is good enough to supply decent oil pressure if its in good condition.
- I'm using 21/47 sprockets which works well enough, with your conversion to 845cc 22/47 may work better. Not sure if you can go any lower on the rear sprocket with the conical hub.

Good luck smile

Last edited by gunner; 10/11/20 9:25 pm.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: A65 + A10 crank = advice requested
S-NJ-W #826222 10/11/20 6:23 pm
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Hi Steve

If your buying the barrels from Ed V, then why not have him convert your crankcases to Needle/ball and end-feed the crank. Then your oil pump (refurbished) should be more than adequate for the job. To get the best out of you 845 you would at least need to go to 30mm carbs, most likely 32mm and preferable use larger inlet valves.

As I said have a word with Ed V first it will be money well spent.

Hope thats of some help

John

Re: A65 + A10 crank = advice requested
S-NJ-W #826226 10/11/20 7:23 pm
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I’m doing/done the same conversion as you in a 71 frame.

My reasons for starting the build were to have a decent mile muncher that the misses could sit on the back of, loaded with luggage and possibly a trailer also, have bags of low end torque so that I’m not having to rev the motor to get anywhere. Also be able to gear the bike up so that I could keep the revs down at 70-80 mph.

Since starting the project, my girlfriend has become my wife-to-be and we have a baby girl and I’m not fitting a side car anytime soon (I’ll buy an M21 when I decide to do that). Anyway the project goes ahead.

I’m fitting the “A50” cam, it’s the same cam profile they fitted to some of A10 super rockets, all the gold flashes and the early A65. It’s a good cam! Not the most spirited cam, but gives enough torque. I believe if you buy the mega cycle X2 which is the one your referring to. I’ve retarded the standard spitfire cam and it’s worked well, but it’s given the bike a lot of poke and acceleration, it’s not what I’d be looking for in a cam for this project but you might? However if I was going to buy a sportier cam I’d buy the SRM race cam. It’s better all round and much cheaper than the mega cycle (I’m using the X12 at the moment and I’m not over enthralled compared to the SRM cam when being used on my 650)

My 823 motor (79mm bore) isn’t end fed, the journal was sleeved and the drive side altered to take the Bob Newby primary drive pulley, and except the alternator rotor, the id of the A10 bearing is larger so this needs to be machined down if using the A65 bearing. If/when I do another I’ll consider it being end fed

I’m not after big compression either with mine, I’m using a John Hill aluminium (Nicosil coated) barrel and he supplies two gaskets for the job. I believe the SRM barrel has sleeves fitted? Either way you will have to work on the crankcase mouth for the barrel to fit. I felt Johns was the better option and better value for money.

Because I like the oif thunderbolts, I’m fitting this Lightning with the single carb head, I’m also sticking with the 928, again this with the smaller ports will improve bottom end, I have no intentions to open the ports out.

Your jetting will be more subjective to air filters and exhausts, I believe the A70 had the same jetting as a lightning so this should tell you something. If it was my money I’d stick with the 30mm carbs and leave the ports as they stand. I would look at getting an OIF head though. What you have there is a c1966 head, hence why there’s no rocker cover head steady. It’ll work fine but oif heads start 71- there was 2 twin carb heads made... the one which has the pushrod section cut as though it was taking the pushrods into consideration (or rather looks like some one has taken a bite out of it) is the better head, the other type has slightly different shaped ports and seem to be of a poorer casting. I have both although tucked and buried behind a frame that’s coated with paint stripper at the moment.



Gunner, I have the same question as you regarding rear sprocket. Afaik 47 is the smallest rear. The BNR clutch will add equivalent to 1tooth at the gearbox (my Lightning is like this and pulls it fine) so I’d be looking at fitting the 22t gearbox sprocket with this setup. It’s as good as 2t taller than the A70 for me. I also saw on one of the Facebook forums one fella cut out the trap door to take the 22t sprocket! And it worked and sealed fine. So I’ll be looking at doing the same. I’m not worried about oil leaks as the BNR is a dry clutch.

Hope this helps. I’ll try and post some photos later


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826240 10/11/20 9:09 pm
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I have an A10 crank in an A65, the DS end will need work to take the Alternator rotor. cases will need work for barrel spigot clearances and flywheels. I used Triumph pistons and overbored stock barrels to get 770. Its not my favourite, the short std stroke motor with big bore to 732 is much smoother and revvier.
You cannot go lower than 47 on the conical rear, a 22 tooth sprocket and 47 rear will put 60 mph around 3,500, if you want less revs you will need a different rear wheel, the later T140 disc type will give you more options.
+1 to Johns post, EDV is yer man.

You want/ need the head steady, look for a 71 head, you will have a fun time trying to get the head on if the barrels are taller than stock, there is not much room under the oil spine. With no head steady it will shake badly. The head clearance may be a non issue , bigger bore pistons have a lower pin to crown height, B44 type is what usually go in.
keep the stock cam, carbs 32mm .

An outrigger bearing to replace the seal behind the clutch is a very good idea, especially with 200 ccs more.

Plan for a Disc conversion to the front end, you will need it


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 + A10 crank = advice requested
S-NJ-W #826244 10/11/20 9:49 pm
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Chaps, thank you very much for the replies so far.

Gunner - I lived in Strood, the girlfriend was in Maidstone and I was a student at Medway and Maidstone Tech College.
I am very familiar with that hill, up and down! smile Well, I was some time ago. It's been a'while. Bluebell hill too.

Yes, I should have mentioned I am planning on adding a Commando type spin on filter in the return line.
Adds to the total oil volume as well, that I perceive to be small. The manual says 5 (imperial) pints in the frame.
That can't be true.

Agreed, I don't know if I can go any smaller on the rear sprocket, given the bolt spacing on the comical hub.
I was wondering if anyone had done it. I can start out with the 22/47 setup and adjust from there, if possible.
If not, then it is what it is, so to speak. Is a 23 tooth gearbox sprocket available?

John, I didn't know that E&V offered that conversion. It's not on their web site. Thank you for the pointer.
Yes, I will talk with them before proceeding and spending engine money.

Just to touch on the carbs and the head a little - Yes, it has 930's (L&R) but the intake ports are 28mm.
The least I can do is get the transition between the carb and the head smoothed out. Should I get the intake
enlarged to 30mm ? A pair of 32mm AMAL's from an 850 Commando are in the loft, somewhere.

Allan, thank you also for the reply. Good to hear you are attempting a similar conversion.

I think I understand that you sleeved your A10 crank timing side main journal up to A65 dimensions
(1 3/8 to 1 1/2). Right ? Are you confident of the sleeve? That would give me the heebie-jeebies.

I plan on getting a bush turned up to A65 outside spec, so it fits in the A65 cases, but A10 inside diameter,
plus a bit oversize so I can bore it to fit whatever the crank turns out to be when ground.

I am not sure I understand your comment about the drive side bearing. I think they are the same, as both
started off as 67-1240, but may well be mistaken. I am guessing I am going to have to make a spacer to fit
the alternator rotor to the A10 crank.

In terms of cam, I have the standard of whatever was fitted to the A65 in '72. I thought it was the Spitfire from '66.
Once again, not looking for top end RPM, just as much 'grunt' as possible up to about 85ish on the 'new' gearing
(say 22/47). You think the SRM race cam is the way to go? Yes, the MegaCycle cam is expensive. In the order
of $500+ I think.

I plan on keeping the compression ratio at or less than 9:1.
Memories of starting my 10.5:1 B50SS come flooding back..

You touched on the clutch, which I recall being a bit 'iffy, even on a 650. I was going to use the SRM 7 plate
conversion and spring plate with a bearing, instead of an un-lubricated ball bearing. Any opinion on that?

Do I understand you have gone to dry belt drive? I am impressed! How is that? How is the heat dissipated?

Again, thank you for the welcome and the replies. If feels good to be among friends, just coming back into
BSA ownership.

S.

Last edited by S-NJ-W; 10/11/20 9:53 pm. Reason: spelling, clarity.
Re: A65 + A10 crank = advice requested
S-NJ-W #826246 10/11/20 10:04 pm
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Gavin, thank you also for the reply. I already have a pair of T140 fork sliders and plan to replace the standard BSA
front end with a disc.

The '71 head is very different? To take the head off the bike I have, I had to remove all of the oil spigot for the rocker
feed and unscrew all the 'studs' at the back of the head just to (slowly) jiggle it off! Yes, it's very tight in the frame.
I was planning on replacing the studs with Allan screws. I can live with that.

Good to know you have an opinion about the head steady.

Here is my calculation about rpm/mph through the gears at 22/47:

4th 3rd 2nd 1st
1000 rpm 17.5 15.3 10.9 7.0 mph
2000 35.0 30.6 21.9 13.9 mph
3000 52.4 45.8 32.8 20.9 mph
4000 69.9 61.1 43.7 27.9 mph
5000 87.4 76.4 54.6 34.8 mph
6000 104 91.7 65.6 41.8 mph

I would like less rpm at 70 in 4th.

What balance factor did you use for your crank? I think I am looking at 50 to 60.

Last edited by S-NJ-W; 10/11/20 10:05 pm. Reason: formatting
Re: A65 + A10 crank = advice requested
S-NJ-W #826247 10/11/20 10:06 pm
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Messed up the formatting..

Re: A65 + A10 crank = advice requested
S-NJ-W #826250 10/11/20 10:27 pm
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> An outrigger bearing to replace the seal behind the clutch is a very good idea,

I will need to research that. Not heard of it before.

Re: A65 + A10 crank = advice requested
S-NJ-W #826252 10/11/20 10:39 pm
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Sorry to break this in to bullet points, I use Britbike through my phone and it means a lot of scrolling around.

The sleeve, yes I have a lot of confidence... or at least I have a lot of confidence in the guy that did the work. The end fed conversions are all sleeved, providing you have some oil then there isn’t an issue. BSA fitted a 70 or 75psi OPRV to the A70, I will look at doing the same. As Nick L pointed out in an earlier thread if you go end feed, stick to the 50psi otherwise you’ll stand the risk of inverting the oil seal on the quill.

Gavin mentions altering the barrel to clear the A10 flywheel. If I remember correctly the A10 flywheel has a 5mm bigger diameter (I don’t think it’s radius hmmm) I had the chap who did the work on mine to machine the flywheel to match the one on the A65. Worst case scenario is fit a decompression plate. At 845cc it’s going to be a beast to kick start! Which is the only reason I’m going low compression, least until someone releases an electric boot onto the market.

Having a bush made to suit might be fine but it might also carry some other problems. The A65 uses a thrust washer for the endfloat. On the A10 crank there is nowhere for this thrust washer to face on to. The sleeve I have is a top hat which includes a thrust face as part of it for the thrust washer. I’m not sure how this was done on the A10. Been a while since I’ve looked inside one.
The other thing to note is the crank is smaller on the A10. Unless you plan fitting an outrigger bearing to control the endfloat... you will need a way of keeping the crank centralised between the bores.

I think a 22 to 24t sprocket is available from SRM. Although I need to look myself to order mine. I’ll get back to you on that. At 845cc with 22/23:47 it’ll have more than enough grunt.

Cam: your right it was the spitfire as standard from c66. But not on the A50. 68-103 from memory and 68-473 for the spitfire. Both will be fine. I just know the A10 pulls really well on the standard cam, 200cc more and you’ll get more of a good thing in my view. If your changing completely from standard then go for the SRM. With your ports as they stand it’ll pull from really low down and it’ll keep revving also in a high gear. This is what I found. The down side Is drop the clutch in first and it’ll pick the front end up.

Cylinder head: I’ll try and find the service sheet that BSA did for the spitfire when they switched to 32mm Concentrics. Instead of porting the whole port, just open out the first bit. You could go further and do the same as mark Parker has done with his... but tapering the port worked for BSA on numerous bikes: spitfire, Lightning (clubman) but also on the 64/65 Lightning’s and the Late Goldstar.

The clutch is a topic of diversity. A lot of people like the 7 plate clutch. I had this with an SRM pressure plate. The more power I generated the more I had to do to make it grip. I eventually got it sorted but I’d already bought the belt drive. And it cost me less in the long run with the belt drive unit.

I fitted the Bob Newby as mentioned previously. Personally I think it is superior to the Hayward etc kits. It does run dry and the complete arrangement is replaced. The clutch is a single item unit (there’s about 70 ball bearings for the clutch on a big wheel. The centre is in one piece and the whole item comes on/off as such. It’s handy if your changing sprockets. Remove the 6 clutch springs, undo the main shaft nut and a sliding jaw puller gets the basket off. Just slide it out from under the belt and that’s it. There’s no tensioner used either. Doesn’t need it.
Heat isn’t a problem but Bob mentions making a way for moisture to escape. You have the tensioner bolt removed so that’s one way. You can either cut a fancy pattern in the primary cover or fit one or
Two of those fancy vented inspection caps from eurotrash jambaylia website which is what I did on the Lightning.

Attached Files 75F4DD8C-9C8D-477C-97E0-1F38550A70E2.jpeg713DA66E-D1ED-4F7B-8463-5C07B8EB4BE2.jpeg86747A54-8A27-4A54-ACEE-D4BCC9146FC8.jpeg23F87577-211E-4E1B-B937-34281F1F2FD4.jpeg790F5F6A-F037-4198-A50A-8948A192109E.jpeg
Last edited by Allan G; 10/11/20 10:45 pm. Reason: Added photos

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826254 10/11/20 10:50 pm
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SRM did my crank work , i dont know the balance factor , my A10 /65 is in a Norton frame, the factor for this would be different from the OIF any way. i told SRM it was going in the Norton frame, its not bad / not that smooth either.
Speak to Ed V about BF. I strongly recommend the end feed/ ball roller conversion, it is a much more robust arrangement with more oil flow to the big ends, the crank is trapped , no endfloat, smoother. This comes up regularly , Nick L and others will chime in and say the bush is fine.
You pays yer money takes your choice.

The 71 head has a bigger rocker cover gasket face, 5/16 fasteners with longer threads and cast in mount for the head steady. an earlier head will fit , and if you weld a bracket under the steering head you can fit a head steady on the older centre mount.

Big inlet valves are a good idea, the ports can be modified by filling the floor and giving the m a D profile, search for Mark Parkers work.
I can give you rough carb settings for 32 s, 220 MJs 106 NJs , 3.5 slides will get you in the ballpark

Last edited by gavin eisler; 10/11/20 11:03 pm.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 + A10 crank = advice requested
S-NJ-W #826255 10/11/20 10:54 pm
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Some more images

Attached Files 5817BE1F-A8D0-4519-852E-EBF91C50725C.jpeg3F71D989-C074-4238-8ECC-3CEF6BD31232.jpeg

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826256 10/11/20 11:03 pm
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The better way is to use a norton 750 commando crank and turn up a flywheel
preferably at 90 degs offset. It's a fair bit more machining work though.
The A10 crank is not as strong as the standard a65 crank that's why beeza's
made a different crank for the a70.
Nourish used to make an 85mm crank for the a65 that would be an excellent option.
30mm carbs will be fine for the road. Standard 'spitfire' cam.

Stick the whole lot in a box and get E&V to quote for the job.
You'll be up for:
Rods
Pistons
End feed conversion
Oil pump overhaul
bearings
Barrel
Gearbox overhaul
7 plate Clutch
Pressure plate
Refurb the carbs.
Gaskets
Sprockets
Cylinder head ('71+ type)
Cylinder head overhaul including valves, guides, springs etc.
Gearbox outrigger bearing and plate

Kevin on the triumph section of this site listed a bloke who has some nice
84mm cranks done for a65's can't remember his name though. Nice job
but not a budget item.


Go out and buy a late Moto-Guzzi it'll be cheaper!


And bye the way Gavin, when fitting a different crank, yes a needle race is the way to go,
i just don't think it's required with the standard engine.

Last edited by NickL; 10/11/20 11:25 pm.
1 member likes this: gavin eisler
Re: A65 + A10 crank = advice requested
S-NJ-W #826257 10/11/20 11:25 pm
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BSA service sheet

Attached Files EEAB2F9C-870D-454B-8F46-BE8E658D2966.jpeg

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826260 10/11/20 11:50 pm
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Note from Kevin, these are a very nice job. He does an a1/a65 one as well


https://www.yellowpages.com/plymouth-mi/mip/rody-machining-6041454

greg blagus. he makes flat track cranks for BSAs and triumphs. he starts wiyh a blank T140 crank and then cuts it to fit whatever bearimgs youre using. i had to have him narrow mine to fit into T120 cases. its been inside two engines now


theyre expensive. $1600 plus custom balancing. but like i said, its a forevrr crankshaft that will last the life of the machine without any diffivulty at all.

even if this isnt what yoore looking for, you have a price now for a top of the line crank to bargain with when somepne tells you his unit is the best there is

Re: A65 + A10 crank = advice requested
S-NJ-W #826261 10/11/20 11:51 pm
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id rather have an old motoguzzi, an earlier lemans wouls suit me

the billet A10 cranks come from greg blagus of rody machining. plymouth michigan, iirc. hes a friend of ed v and lives more or less nearby


I would rather be ashes than dust
Re: A65 + A10 crank = advice requested
S-NJ-W #826264 10/12/20 1:37 am
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Blagus was the go to guy for stock car and drag race cranks.Carburetor Guzzis are great affordable bikes for distance riding. Better handing than BMW's .Thundering down the road on big bore Italian V Twins it's not so much you are moving as the bike is stationary pulling the world towards it...


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
1 member likes this: Nick H
Re: A65 + A10 crank = advice requested
S-NJ-W #826278 10/12/20 6:37 am
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Quote
I lived in Strood, the girlfriend was in Maidstone and I was a student at Medway and Maidstone Tech College

We must have passed like ships in the night as I lived in Rainham and had a girlfriend who lived at the top of Bluebell Hill.

Regarding the sprockets and gearing I believe there is a 5 speed box available, I think Jer Hill who posted earlier was selling them a while back. I dont know what the ratios are but maybe slotting in 5 speeds instead of 4 would help.

Last edited by gunner; 10/12/20 6:38 am.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: A65 + A10 crank = advice requested
S-NJ-W #826280 10/12/20 7:06 am
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Hi

I'm not sure you want to go with the 22t G/B sprocket. I'm running a 21t on my 845 and put a 50t rear (could have used a 20t G/B, but was to lazy to strip the clutch off) to make it a little better at low revs in 1st. and it still does 80 at 5k rpm. Although my primary gearing is a little higher and running a 5 speed gearbox so its not the standard std set-up.

Using an 84mm crank and B44 pistons will make the barrel base to head height more or less the same height as a std 650 height. If your 72 cam is Ok, just use it, unless of course you go 90 degree.

The fact that you need a late type head in order to get the correct rocker cover to give you a head steady is good. and gets you away for this 28mm inlet. You are adding 100 cc/ cylinder you need to let that engine breath, sorry to disagree with all the small port gurus, Go look at some off Mark Parkers posts on porting. If you want to email me at [email protected] I'll send you a spread sheet on the ratios you can play with.

my tuppence worth

John

1 member likes this: gavin eisler
Re: A65 + A10 crank = advice requested
S-NJ-W #826286 10/12/20 9:17 am
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On cam choice , gearing and revs.
My 732 big bore has the 21 tooth sprocket 47 rear, and stock late "Spitfire " cam timing, the motor starts coming on the cam and puling hard from around 3.5 K, I wouldnt want gearing that put my cruise speed below these revs. For a super soft motor you could put in the pre 66 cam for less top end more mids, combined with flat top pistons, stock valves and a single carb this would give a nice smooth stump puller but it would lose a bit of sparkle at higher revs.

I often find my self changing up when I am already in top, but I know if I fitted taller gearing I would lose on acceleration and hit a brick wall of wind at higher speeds, 21 47 is a good compromise for me.
The 732 has a load more middrange than a stock 650. For a fun smooth road bike its a good option.

Past experience with A10s and different cams, with a chair on the side the less hot cam was a lot easier to ride .


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
1 member likes this: Allan G
Re: A65 + A10 crank = advice requested
S-NJ-W #826296 10/12/20 10:52 am
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Chaps, thanks for all the replies. Good advice.
Great pictures Allen.

To try and constrain what appears to be rapidly escalating pricing around billet, built up, 90 degree crankshafts and the like, lets keep with what I have. An A65, a A10 large journal crank, a 66ish twin carb head and a willingness to spend some, but not a small fortune.

Lets stick with 30mm carbs and smooth out the ridge between the head and the carbs.
Keep the inlet valves as is.
Keep the A10 crank, but acknowledge it's limitations. 6k rpm is the redline.

Keep the notion of a 'standard' timing side main, but running in a custom bearing that accommodates the smaller A10 journal in A65 cases. Maybe an A70 pressure valve.

A big bore kit from E&V, now almost a requirement, because it's doesn't raise the cylinder height, now a critical dimension as pointed out by Gavin, because of the pre 71 head in the OIF setup.

Can we discuss how to set the end float?
I had 'assumed' I can use the A65 thrust washer and set end float by the standard method of shims between the drive side crank cheek and the roller main. I anticipated setting that close, maybe 1 or 2 thou when cold.

I should add that I have a lathe in the garage, big enough to swing the crank and a mill, big enough to fit the cases, on their side, under the head.

Gunner, I used to attend college with the lass whose family ran the newspaper shop at the top of Bluebell hill, before it was dual carriageway. We used to sit outside at the Upper Bell and admire the view. I also had a number of friends in Rainham, in and around Otterham Quay Lane. We would use Mearsborough Road to take us up to the M2 services and join the motorway there.

Steve.

Last edited by S-NJ-W; 10/12/20 11:05 am. Reason: spellin. dyxlexia ruls, ko.
Re: A65 + A10 crank = advice requested
S-NJ-W #826303 10/12/20 12:11 pm
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There’s a lot of A10 cranked A65’s that run perfectly fine.

It’s seems to me that your after a bike with a lot of low to mid range but not bothered about top end. I think the setup you have will give you that.

I’m not a metallurgist, so this next bit is more guesses and assumptions...

My machinist machined the web flat before fitting the top hat sleeve. I wanted it sleeved to fit the A65 bush. If you look back on Servodynes post about his A70 build, what I did was similar but not the same as what he did. You might (I use the term loosely) be able to have a bush made like the original BSA design but with a thicker steel cage then have the sleeve to fit instead of making it all out of one? Possibly have the sleeve made with a top hat to incorporate a thrust face, so thrust washer and sleeve are all in one? I don’t know if this is good or bad engineering practice.

I am impressed with what was done with my bottom end (ooh er) but it involved a lot of R&D as well which wasn’t cheap. So I don’t know how much it would cost to do it again.

Would I do it again... Yes I think so already... would I have it end fed instead... probably I would but the next motor will be a 750 and use the V.high compression pistons that I already have.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826309 10/12/20 2:26 pm
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1. If you're going to use your existing head and valves leave the ports alone and do not smooth out the ridge between carbs end ports, it's very small anyway and will work for you with some extra gas turbulence. I know it worked for me. I have 32 carbs on my small port head ( 27 mm dia. ) and with stock Spitfire cam and stock valves from big port head ( which I believe you have ) gave very good performance with lots of grunt at lower revs and better high revs to. Somebody knew what he is doing changing a head, or was it by accident, but this conversion is checked and true and gives you better performance in stock 650 engine.
The difference was so big I decided against bigger block conversion and concentrated on better brakes / suspension realizing my bike getting faster then I used to be.
2. I don't think you need 22 gearbox sprocket, 21 is big enough and gives nice acceleration with bigger engine, every tooth added to a front sprocket is a big change in gearing, so +1 to what Gavin said - 21 / 47 should be good in your case.
3. To have a front disk you need complete front end from T140 / T150, they are wider than conical front end and triple trees and stanchions are different. Or different Japanese front end.
4. Check your existing rods for ovality, if oval just change them to MAP steel rods - it's good investment in BSA engine.
5. 5 gear's box from J. Hill would be great addition, expensive but IMHO much better addition to the bike than any extra machining to get more power from your engine. If you had some extra money to spend this is the goal worth spending. I have 5 speed in my Trident and see the difference.
6. You need 3 phase alternator + 3 phase reg rectifier to have a proper base to build your charging system on.
7. With bigger engine you will have some method to tackle vibrations, perhaps they won't be as vicious with a longer stroke of A10 crank.
8. Try to lower compression of Ed V. pistons, in your case it doesn't help much but makes vibrations stronger.

Last edited by Adam M.; 10/12/20 2:36 pm.
Re: A65 + A10 crank = advice requested
S-NJ-W #826327 10/12/20 6:10 pm
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You might find this Link (click here) interesting. A guy has done a similar thing to what you (we’re) doing. A10 crank and 79.5mm B44 pistons.

I skipped a lot of the article and went to the end, most interestingly he’s using the BNR clutch which as mentioned previously is like adding a tooth at the gearbox. But he is also using a 23t front sprocket and a close ratio box. I have to say this will make first a very tall gear which is why I didn’t plan on going above the 22t with the BNR. however this owner/restorer must get on with it fine.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
Adam M. #826328 10/12/20 6:19 pm
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Originally Posted by Adam M.
1. If you're going to use your existing head and valves leave the ports alone and do not smooth out the ridge between carbs end ports, it's very small anyway and will work for you with some extra gas turbulence.

Adam, have a read on Roland Pikes development of the gold star and you will see why they fitted that slope to the Goldstar, small
Port A65 heads and spitfire head as shown in the above article.

Something you might find Interesting to experiment with Is to get some thick Tufnell spacers of about 28mm (1 1/8 is actually 28.5mm so you need to open them out a little to start with) you can either mount the spacer in a lathe if you’ve made a mandril to hold it or use a file/Dremel etc and slope the spacer (10mm thick spacer would be best if thicker Still) to match the port (which is already slopped from the mouth at 28.5 to 27mm) And try the bike like that. Then take those spacers off and turn them around so the tighter end is facing the carb. I think you’ll find the slope is an improvement.

You want to create a Venturi in the port to speed gas flow, turbulence slows it down.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826332 10/12/20 6:38 pm
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Allan, after reading Roland Pike memoirs and his "experiment" with bigger carb attached to smaller port I decided not to touch them and was very happy with a result. In SNJW case it's only 1mm sidewise, mine was 1mm going to 2.5 with a port slope. Actually he can try both possibilities using your idea of tufnell spacers.

Re: A65 + A10 crank = advice requested
S-NJ-W #826346 10/12/20 8:13 pm
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Allan, Roland Pike found more power with the step than without.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 + A10 crank = advice requested
S-NJ-W #826355 10/12/20 8:54 pm
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Link to the memoirs... Maybe I have misread it but either way, they didn’t fit tapers to the start of ports on A65 heads just for shits and giggles.

https://www.yumpu.com/en/document/read/2590194/roland-pikes-bsa-memoirs-20-11-01


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826363 10/12/20 9:23 pm
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Read chapter 26 ignition and carb topics.To summarise, By mistake an oversize carb was fitted for a dyno run, a power gain was noted .As soon as the port was opened to match the oversize carb all power gains disappeared,


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 + A10 crank = advice requested
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Your not telling me anything I don’t already know Gavin, I’ve read those pieces word for word many times. Further on in the section it notes about a Venturi no less than 80% the size
Of the carb. ...Blah blah blah... using the typical angles of 22° and 7° Out...

I may have mistakenly understood this as being the angle on the head being one of those, I say maybe I have because there are some inlet systems which use those angles tapering down to the carb going in and opening up from the carb coming out. Although we know the Goldstar doesn’t use this.

Annoyingly I can’t copy the text off that link on my phone. But as I say they didn’t start doing this on the unit twins just for the sheer fun of it. They also did it on all the thunderbolt heads and on the early twin carb A50’s (cyclone?)

Originally Posted by gavin eisler
Read chapter 26 ignition and carb topics.To summarise, By mistake an oversize carb was fitted for a dyno run, a power gain was noted .As soon as the port was opened to match the oversize carb all power gains disappeared,

They sleeved the port back down to size again. I’m not talking about opening up the port, just the mouth of the port as per the service sheet. This would be difficult to sleeve I would have thought.

I don’t want to derail from the original topic. But if you have something to show visual that proves different then it will be interesting to discuss further.

Last edited by Allan G; 10/12/20 9:51 pm.

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826373 10/12/20 10:34 pm
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Chaps, thanks for the discussion. Clearly, it's easier to keep the step between the head and the carb.

The advice about using the spacing washer to test with and without is invaluable, but it's only 1mm off the radius on the current carbs. I do have a pair of 932's from a 850 Commando that I could dig out, maybe once the 930's and the rest of the engine are up and running.

It may very well be that the previous owner was aware of the potential benefits of the small port head. He clearly went out of his way to find and fit one. Alternatively, it might be happy coincidence. But he fitted both the small port head and sourced a (left and right) pair of 930's (jetted to factory spec) and a twin carb airbox then fitted it all on to the A65T. Dumping the '71 spec head steady, head and single carb on the way. The fact he dumped the single 928 rather than add a left handed 928 to the set up might be the indication that he knew exactly what he was doing. Hard to say.

Adam M, thank you for the heads up about fitting a disc to the front end. I had naively assumed that all that was needed was the correct front wheel and the appropriate fork sliders, caliper etc. Now you point it out, the disc braked front wheel is indeed wider then the conical hub. I will need to find the correct yokes for upper and lower.

Allan G, it looks like you have done that conversion on your A65 and retained the wire headlight brackets. I will start a separate thread about what's needed to do that, rather then intermingle it all here. I would like to just keep the focus on the work needed to the engine to add the A10 crank in this thread.

Can I bring us back to the subject of crank end float.

Most A10's had NO end float, by the fact the big spring that was the transmission damper was screwed to the crank and held it tight to the drive side crankcase.

Looking at the photo provided by Allen G of his conversion, the sleeve used to bring the A10 timing side main journal up to 1.5" from the standard A10 size of 1 3/8, has a 'lip' on it that must have been specifically turned and dimensioned to control the end float.

Allen G, do you know what your end float dimension was set to? Standard A65 has a thrust washer on the timing side and a number of shims on the drive side and you are encouraged to set the end float to 3 thou. I can skim the timing side of the A10 crank to be flat on axis and smooth to interface with a standard thrust washer then shim the drive side in the same way. This is exactly what I was planning to do, but setting the end float to more like 1 thou when cold.

Again, thank you for the heads up that the A10 flywheel needs to be turned down to enable the barrels to fit. I will have to 'test' assemble the big pile of bits sitting on the workbench. It sounds like Allan G had the flywheel reduced, but Gavin slimmed down the barrel flange. The disadvantage to machining down the flywheel is that you disturb the balance setting that was set by the factory. You can see that Allan's flywheel has had a number of (new) holes drilled in it to reset the balance factor. The higher the balance factor, the smoother the engine is at high rpm, not at low, and vice-versa. Because I don't plan on revving the nuts off the A10 crank, I plan to go for a lower than standard BF.

Let's agree that we can keep the gearing at 22/47 for the time being, as I am dubious that a 21 tooth Gbox sprocket is going to drop the rpm's enough to both keep up with traffic and not cause the thing to fly apart. If that turns out to be too high (especially 1st gear in traffic) then I will bite the bullet and put a 50 tooth rear wheel sprocket on it from an A75 or the like.

Thanks for the insight.

Steve.

Re: A65 + A10 crank = advice requested
S-NJ-W #826377 10/12/20 10:49 pm
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If you are going to use the 60 year old A10 crank, have it crack tested x-rayed
Then nitrided or tuftrided.
I've recently used an a10 crank in an a65 race engine, the crank was like brand new
but i'm still not that keen on him doing more than 6500rpm with it. I wanted to use a
norton crank but that involved special rods and would have been another couple of
grand to sort out plus he had the A10 crank.
By the time you've messed about making a special bush etc, you could have done a needle
or combination bearing conversion anyway. I suppose it's how much of it you can or
want to do yourself. End feed setups aren't the rocket science they are often referred to as.
Avoid any welding and it's straightforward enough.
You will have to balance the crank again in any case, start at around 65%.
You can use the a65 flywheel on the A10 crank but it will still need balancing.
The crank end float will be set up in the same way as your a65 if you use a T/S bush
but as Allan says you may need to put a thrust face on the crank and make a washer to suit.

Last edited by NickL; 10/12/20 11:41 pm.
Re: A65 + A10 crank = advice requested
S-NJ-W #826380 10/12/20 11:03 pm
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Thank you. Yes, I was planning on having the A10 crank crack tested before doing anything else to it.

Because Austin Texas is home to the F1 COTA race track, we have a number of competent automobile engineering shops in the area.

I can make the bushing myself. As I said, I have a lathe in the garage big enough to swing the crank between centers and a mill big enough to get the cases under the milling head.

Steve.

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A couple of thou end float is all you need. It grows as the motor heats up.
Make sure the crank is central when setting up.

Re: A65 + A10 crank = advice requested
S-NJ-W #826406 10/13/20 8:25 am
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The end float as Nick has already told, is set to about 2-3 thou from memory.

I’m not sure how thick the thrust face is on the top hat sleeve, and this will vary a little I guess depending on how much you take off to clean the web of the crank and how much you then need to get the crank central.

Regarding the balancing, the piston size has increased about 10mm from the original A10 piston although the piston is probably not as tall. In the 50’s I don’t think the factory did much in the way of balancing either, they did a lot on the later A65, moving location of where the balanced late 60’s then the very last ones had scalloped flywheels like the A70. I asked the balance company to have mine best around 3-4000 revs.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826415 10/13/20 12:13 pm
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This sounds like a great project and has created much interest judging from the number of posts! A couple of comments. Supposing that your motor works out well, you will probably need a different clutch. As Allan mentioned the BNR is a very good and trouble free unit and you can use the standard charging system with it. At the least the transmission will have to be in perfect shape in order to stay in gear with the torque of the big motor. The 22 is big. I just put it in before assembling the cases. Then you can adjust at the rear as needed. The head steady is a vital part of the package. I have seen and experienced the damage from no or misapplied steady. Maybe someone here has done some work adapting an earlier style steady to the late frame. Save your money on the cam. If your stock 473 is in good shape it will work fine. Get some good, non racing, springs from Ed V.. Have fun, PRT

PS We have relatives in Austin. Whenever we can get down there maybe visit?

1 member likes this: Allan G
Re: A65 + A10 crank = advice requested
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Thanks Tom.

Yes, I came come to the realization that I will start off with the 22/47 gearing combo and tune from there via the number of teeth on the rear wheel. The issue becomes how high 1st gear winds up.

I don't have a lot of slow traffic around me and the major focus was trying to keep up with modern traffic speeds without hitting the onset of major vibration. I remember my original '69 A65L was spinning at about 4200rpm to make 70mph and that also marked the onset of significant vibration. I was trying to use the torque of a bigger motor to push the gearing higher to keep me out of the vibration 'band' while riding at between 70 and 90 (which are normal speeds around here).

I remember the clutch often requiring attention on that previous bike. My plan is to use the SRM 7 plate conversion and plate with a thrust bearing. That's not crazy expensive and I can ponder what to do if it starts to slip. At least I now have the tools I need to get the release plate lifting square!

The older bike was hard in traffic, as I used to be in South London a lot with it. Having the carbs bolted to the head with no heat shield made the petrol in the float bowl evaporate, which caused you to blip the throttle to keep it running, which made the problem worse. Then the clutch would start to play up. I remember parking it to cool down outside Pride and Clark's, while I took a slow look around. There is an active thread on the board about this, right now. I tried putting phenolic spacers on the carbs but then couldn't get the round chrome air filters to fit without hitting the side covers, which kept falling off anyway, because the Oddie screws were so loose. Those were the days. Playing chicken with the traffic on the A2 to pick up your oil tank cover..

I am not sure what to do about the head steady. The frame and other large bits have gone off to be powder coated, so I can't trial fit the engine back to the frame to mark where to weld a bracket to attach a pre '71 style head steady. Assuming that I can get the big block conversion cylinder to use the twin carb head I have *and* get it all to fit in the frame, that's the current plan. If not, I will be looking for a post '71 twin carb head, which is not easy to find.

Yes, if you are ever in the Austin area, hit me up. I am out by Lake Travis. There are a lot of Brits in the area, by virtue of ARM's HQ being just down the road. I have been here for more than 20 years now and like it a lot.

Re: A65 + A10 crank = advice requested
S-NJ-W #826426 10/13/20 2:22 pm
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Can I just add to the conversation the comment I made about the previous owner and the small port head :

>It may very well be that the previous owner was aware of the potential benefits of the small port head.

This bike hasn't been on the road since 1981. This may be a shock to some of us, but that's almost 40 years ago.
Off the road for 40 years. 40 years!

I am guessing that the previous owner fitted the small port head, 930's and twin airbox *before* 1981.

It looks like a wiring fault took it out of use.. There was no main fuse, that I could see. I also think the
battery was badly damaged by the look of the battery carrier and petrol tank (!)

The internet, as we understand it, wasn't in existence at this time.
I was still writing assembler code on punched paper tape. Well, sort of.

No BSA forums to discuss such things. Was the benefit of small port heads widely known?
I wasn't aware of it until reading the back posts on this board.

Lucky coincidence or informed intention?

Last edited by S-NJ-W; 10/13/20 2:36 pm. Reason: spelling, as usual
Re: A65 + A10 crank = advice requested
S-NJ-W #826489 10/13/20 6:37 pm
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I think first gear is relative to your no snatch lowest speed, this will bear a lot on how power delivery takes place. If you do stick with the standard 473 cam as PRT suggests you could advance the timing by a tooth. The valves won’t hit the piston and it will bring the power in lower down. My Lightning had a mis-timed keyway on the crank pinion. With the marks aligned it advanced the timing by 20° (1 tooth is equal to about 16.5° crankshaft degrees) it ran fine and pulled really well at the bottom end.
If you can place your power that low, you stand a better chance of not having to be slipping Your clutch up to about 20mph or so.

I used to run happily with the close ratio box in my tall geared A65. On runs with large groups I hardly ever got out of first. most of the time I was slipping the clutch and eventually bust a cable. So I fitted the standard box back in for that reason. The bikes got the mega cycle X12 cam in it, so it’s not got much at bottom end.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: A65 + A10 crank = advice requested
S-NJ-W #826491 10/13/20 6:58 pm
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The 22/47 combo comes out at about 7mph for 1000 rpm in first.
If I was running the standard A65 gearing of 20/47 that 1000 rpm is 6.3 mph.
I remember a friend (who lived close to where Gunner is from) had an A10RGS with a close ratio box. That was hard work in traffic..

It doesn't sound like too much of an issue, but these are just numbers on paper at the 'mo. Things might be different in real life.

Yes, I think I am going to stick with the standard cam for the time being. The joy of advancing it by one tooth is that it's easily remediable !
smile

Re: A65 + A10 crank = advice requested
S-NJ-W #826494 10/13/20 7:09 pm
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One fix for carbs overheating is to rubber mount them, use a Mikuni adaptor flange with the correct stud spacing then fit Miks.
Or fit a spigot to the ports and use the adaptor flange the other way round, i have this set up, with later t140 V air box rubbers it fits , just.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 + A10 crank = advice requested
S-NJ-W #826503 10/13/20 7:47 pm
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Hi S-NJ-W,

Quote
Most A10's had NO end float, by the fact the big spring that was the transmission damper was screwed to the crank and held it tight to the drive side crankcase.

Not quite how it works!!
The A10 drive side bearing has a single lip race
The inner race is clamped solidly to the crank by the spacer inner cush drive sleeve and the big nut
The spring is not involved in holding the crank, it just keeps the sprocket against the driving sleeve
Crank end float is set by fitting shims between the drive side bearing inner race and the drive side flywheel
The A10 timing side crank end sits against the bush face without a separate thrust washer

John

Re: A65 + A10 crank = advice requested
S-NJ-W #826612 10/14/20 10:23 pm
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The A10 setup is the same as the post-66 roller A65 setup with
the exception the A65 has a T/S thrust washer sitting in a recess.

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