BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike Sponsor SteadfastCyclesBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorHepolite PistonsBritBike Sponsor
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
hacksaw
hacksaw
hamden, ct.
Posts: 972
Joined: January 2002
New BritBike book out!
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Manuals on DVD (Shipping included)
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 2 of 2 1 2
Re: A65 + A10 crank = advice requested
S-NJ-W #826332 10/12/20 6:38 pm
Joined: Apr 2005
Posts: 1,981
Likes: 10
A
Britbike forum member
Offline
Britbike forum member
A
Joined: Apr 2005
Posts: 1,981
Likes: 10
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.

Support Your #1 BritBike Forum!

Check out British motorcycles for sale: British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Re: A65 + A10 crank = advice requested
S-NJ-W #826346 10/12/20 8:13 pm
Joined: Aug 2001
Posts: 5,464
Likes: 69
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 5,464
Likes: 69
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
Joined: May 2013
Posts: 7,193
Likes: 49
Britbike forum member
Offline
Britbike forum member
Joined: May 2013
Posts: 7,193
Likes: 49
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
Joined: Aug 2001
Posts: 5,464
Likes: 69
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 5,464
Likes: 69
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
S-NJ-W #826366 10/12/20 9:48 pm
Joined: May 2013
Posts: 7,193
Likes: 49
Britbike forum member
Offline
Britbike forum member
Joined: May 2013
Posts: 7,193
Likes: 49
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
Joined: Oct 2020
Posts: 20
Likes: 1
S
S-NJ-W Offline OP
Britbike forum member
OP Offline
Britbike forum member
S
Joined: Oct 2020
Posts: 20
Likes: 1
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
Joined: Jan 2014
Posts: 1,011
Likes: 52
N
Britbike forum member
Offline
Britbike forum member
N
Joined: Jan 2014
Posts: 1,011
Likes: 52
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
Joined: Oct 2020
Posts: 20
Likes: 1
S
S-NJ-W Offline OP
Britbike forum member
OP Offline
Britbike forum member
S
Joined: Oct 2020
Posts: 20
Likes: 1
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.

Re: A65 + A10 crank = advice requested
S-NJ-W #826385 10/12/20 11:47 pm
Joined: Jan 2014
Posts: 1,011
Likes: 52
N
Britbike forum member
Offline
Britbike forum member
N
Joined: Jan 2014
Posts: 1,011
Likes: 52
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
Joined: May 2013
Posts: 7,193
Likes: 49
Britbike forum member
Offline
Britbike forum member
Joined: May 2013
Posts: 7,193
Likes: 49
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
Joined: Oct 2009
Posts: 584
Likes: 7
P
Britbike forum member
Offline
Britbike forum member
P
Joined: Oct 2009
Posts: 584
Likes: 7
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
S-NJ-W #826424 10/13/20 1:43 pm
Joined: Oct 2020
Posts: 20
Likes: 1
S
S-NJ-W Offline OP
Britbike forum member
OP Offline
Britbike forum member
S
Joined: Oct 2020
Posts: 20
Likes: 1
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
Joined: Oct 2020
Posts: 20
Likes: 1
S
S-NJ-W Offline OP
Britbike forum member
OP Offline
Britbike forum member
S
Joined: Oct 2020
Posts: 20
Likes: 1
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
Joined: May 2013
Posts: 7,193
Likes: 49
Britbike forum member
Offline
Britbike forum member
Joined: May 2013
Posts: 7,193
Likes: 49
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
Joined: Oct 2020
Posts: 20
Likes: 1
S
S-NJ-W Offline OP
Britbike forum member
OP Offline
Britbike forum member
S
Joined: Oct 2020
Posts: 20
Likes: 1
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
Joined: Aug 2001
Posts: 5,464
Likes: 69
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 5,464
Likes: 69
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
Joined: Feb 2014
Posts: 747
Likes: 45
C
Britbike forum member
Offline
Britbike forum member
C
Joined: Feb 2014
Posts: 747
Likes: 45
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
Joined: Jan 2014
Posts: 1,011
Likes: 52
N
Britbike forum member
Offline
Britbike forum member
N
Joined: Jan 2014
Posts: 1,011
Likes: 52
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.

Page 2 of 2 1 2

Moderated by  Allan G, Jon W. Whitley 

Link Copied to Clipboard
Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.7.4