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#854125 07/19/21 10:57 pm
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I am wanting to build a stroked A65 so I am maximize all the cc's in the 750 class that I'll be racing at bonneville.

I am looking for an A10 crank is usable condition and am located in Oregon, USA

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bones_bir #854133 07/19/21 11:55 pm
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You would be better off sticking with the standard crank and putting decent rods and pistons in.
Any a10 crank will now be 60+years old and an instant rev limiter. As a 650 with good work on the head
and good compression you'll have a motor that will certainly be up there with most opposition.
The short stroke of the a65 allows revving to 8k which would be a benefit on a solo.
Failing that a 750 big bore kit is a great way to go with these engines. Just money........
Putting an a10 crank in involves doing all the bottom end work, end feed etc plus the drive side must
be machined for the smaller ID bearing. Easier to just do the standard crank up with an end feed and
start from there.
Having seen a few broken a10 cranks in these conversions over the years, if you do go that way, keep
it under 6800rpm.
Just my 2c.

Nick

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bones_bir #854134 07/20/21 12:07 am
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Thank you for your input, but you completely missed the point. Sometime you just have to do something completely ridiculous

Everything you have said is 100% correct, and I am not disputing a word.

However Landspeed racing is about putting HP to the ground. You can do that with revs, or you can do that with the brute force of the stroke.

Running with the throttle pinned for 1.5 miles is brutal on the engine. I do not want an 8000 rpm engine, I want a 6500 rpm engine that puts out that same power.

bones_bir #854137 07/20/21 12:21 am
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This one's a 740 with a10 crank, goes very well.
https://www.facebook.com/matthew.tyson.5621/videos/1672662059601228

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bones_bir #854140 07/20/21 12:34 am
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[Linked Image from images.i.thechive.com]

Last edited by bones_bir; 07/20/21 12:34 am.
bones_bir #854176 07/20/21 11:41 am
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Do you have a link to this article? Looks an interesting read, I have seen photos of this bike posted elsewhere too.


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)

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Look in Canada, the northern border states & UK where thye don't ride that much or that far.
Southern states and places like NZ & OZ are very short of good cranks because they are all high milages by now and every one I had had anything to do with in the past 5 years was badly cracked.
You might even be better off with a new hand forged crank
You don't want it it fly apart at 150 + mph when you are lying prostrate over the top of it .


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Allan G #854192 07/20/21 2:31 pm
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It is just a photostrip that I put together, no article.

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I may have one sourced in Montana, we shall see.

I agree, I am not trying to build a grenade.

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Originally Posted by BSA_WM20
Look in Canada, the northern border states & UK where thye don't ride that much or that far.

Yes, because the British don’t take their bikes and ride across Europe or the full length of the country 🙄

Trying to find a decent A10 large journal crank isn’t easy, trying to find one that is of a price that doesn’t make you think of buying a complete A10 just for the crank is even harder still.

Occasionally they crop up for a few hundred notes or less but that’s not often.

Have you looked into having a crank made? There’s a few companies that claim to do them but not in the uk.


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)

Allan G #854196 07/20/21 2:44 pm
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A custom crank, yes, that is certainly on the table. But if I can source one then I'll likely go that route.

Allan G #854211 07/20/21 4:56 pm
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........................
Originally Posted by Allan G
Originally Posted by BSA_WM20
Look in Canada, the northern border states & UK where thye don't ride that much or that far.

Yes, because the British don’t take their bikes and ride across Europe or the full length of the country 🙄


Of course us Brits don't stray far from home with our leaky old BSA clunkers ohno or do we ?


Truck stop I79 North PA

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clap laughing beerchug

Last edited by BeezaBryan; 07/21/21 1:15 pm.

BeezaBryan




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I have several but I'm on the east coast. PM me if interested.
Miike G


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

MikeG #854243 07/21/21 12:07 am
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Thanks

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If you have one made, do it 90degree, it's around 45% less dynamic load, and maybe that much stronger, the way I work stuff out. But then 74mm is probably better and smoother than 84, or you can fit a Commando crank, 89mm and that's easy to make 90degree though lots of machining and it will vibrate. I'd still use 74mm.

An A10 needs a modified A65 flywheel and something like MAP rods and A70 or B44 pistons.

There is something to be said for running a stock size 650, and making hp from it, a 360 degree needs re-balancing for rpm, strong rods, outrigger bearing on clutch door and crank and efficient head and carbs and exhaust. And oil gauge and end feed is preferable. When it goes fast it's not attributed to size but in spite of size. Drone along at 8000 or more if necessary. The factory ran 500s to 9,000.

A big tuned engine to get hp will still want to rev, You can build for it but the cases will be more stressed.


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Kevin on this site knows a firm in the states that has several special 10 cranks for sale.
They were done for a65 conversions for dirt track work.
Hillbilly bike knows who i mean.
Rodi engineering i think the name was. They are a lovely job but not cheap.
Failing that, you can press a made up thick wall tube through the centre hole and have the crank
nitrided etc. it will better the odds.
Either way you must pay attention to the bottom end, fit 3/8 studs, end feed etc.
Using a Norton Commando crank is stronger but will take the displacement out to 800cc+ so may
preclude you from the class. It also involves more work fitting etc.
an offset crank is definitely the best bet as far as strength and balance are concerned.

By the way, putting horsepower to the ground on a65's is something i've been pi$$ing about with
for thirty odd years and i'm still a beginner.

Last edited by NickL; 07/21/21 7:42 am.
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bones_bir #854268 07/21/21 11:54 am
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OP, Nick could be referring to E&V Engineering in Michigan...give them a call. I have a bike that that ran 133 mph at the LSR track in Maine in the 650 modified production class.It made 57-58 rear wheel hp on the dyno at 7050 rpm, never turns over 6900 rpm at the track, not a radical engine...unfortunately it is a Triumph grin I'm just a shade tree mechanic but found parts that like each other and a guy who knows modern theories on head porting. Pushrod Tom's A65 bike has cracked 130 hp...
Spending a ton of money does not guarantee a ton of power...


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons.."I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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I would be more inclined to go along the big bore route.
For a given BHP at lower rpm you will need to make more torque thus more cylinder pressure. This will put additional strain on head bolts, flange bolts, bearings and clutch.
RPM puts little additional stress on the engine if the crank is well balanced (dynamically)
I would use a 750 alloy cylinder as it is stronger in tension than the iron one, Carillo or similar rods and a Newby or NEB belt and clutch


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It's a frequent topic in high performance engine discussions if high rpm or more cylinder pressue at a lower rpm is more stress... It's the opinion that high rpm is more stressful...The business of reciprocating loads increasing exponentially as rpm is increased


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons.."I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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Originally Posted by Hillbilly bike
It's a frequent topic in high performance engine discussions if high rpm or more cylinder pressue at a lower rpm is more stress... It's the opinion that high rpm is more stressful...The business of reciprocating loads increasing exponentially as rpm is increased

And I agree. Salt is a far different environment than dirt or runways. Not better or worse, just different. I have found that higher RPM floats the valves, slips the clutch and generally does not help when you are wide open throttle for over a mile. not to mention traction, which slips unpredictable on the salt and spikes rpm, so for me, more power at lower rpm is better than spinning faster.

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bones_bir #854351 07/22/21 12:53 am
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That's interesting, power production is quite variable in some respects. I was surprised bigger carbs and more flow through slightly bigger valves actually increased midrange on a stock Firebird. If I understand correctly what is happening if the ports are only around 15-18% bigger but the flow increase is around 50% which means the gas speed in the port is much higher. Even at lower test pressure. I can measure the speed roughly on the bench and measure vacuum in the port with a probe. Then convert inches of water to speed on a chart, provided I'm testing at 28"w. If you can follow that. A porting book has a chart reading to 38"w which equals 400fps. 320fps is what they have you aim for, but: A fully ported high precision cast port as with cars is 320fps for peak power, 330fps in race spec of a production head, cnc ported non production head 340-360fps. F1 style 4valve 380-400fps. So this head in the centre of the port is pulling 46"w and more nearer the valve though it has a hose stuck in it. It's at least 420fps the limit is around Mach 0.5 or 580-640fps after 0.65 power generally drops.

On the bike what that means is response and power even at lower rpm, why that is is because even at lower rpm gas speed is higher as you open the throttle the higher speed has kinetic energy push the charge into the cylinder even after the piston passes bdc forcing more air and fuel into the cylinder before the valve shuts, then a 335cc cylinder can fire 335cc + quantity of charge. Just like having a small blower. You can possibly get the same flow from a much bigger port but it does not work the same because it doesn't have speed and the rising piston can push intake out if it's not pushing in.

The A65 outfit Nick's talking about is making power sufficient to beat 840 920 and 1200cc engines running on methanol with a 750 not revving past 6,800. It no doubt can rev higher but it doesn't need to yet. BSA ran A50s at 9,000 so rpm isn't particularly limited by valve gear. C/molly pushrods are good but I'm not sure what Nick uses. But you need possibly 1000rpm over rev ability so stuff doesn't fail. When that dyno time on the 750 happens we can see the power curve and see where it's going.

With a Norton 89mm crank my road bike was not going over it's peak at nearly 8,000 and it was way off with mixture reading far too lean on the main jet.

I drew my rwhp on this graph for comparison but I expect those bikes were tested at their best.

[Linked Image from i.postimg.cc]


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So how many ride John'O'Grotes to Lands end, all 603 miles of it in winter ?
Where as we do ride MElbourne to Brisbane , 854 miles in winter

How many months do you ride a year ?
comparred to sunny climates like California / Texas or OZ where most ride all year round
And how many ride all over Europe comparred to the number who just rode to & from work which was not likely to be more than 20 miles each way.

Boy you lot get touchy.
I did notice at the National at Halls Gap a lot of people complaining the Saturday ride was way too long where most locals considered it too short.
For 2 years I rode 75 mies each way to & from work every single day and there were people who rode / drove further than me.
Back in the 60's 30,000 miles was considered the AVERAGE distaance ridden yearly in NSW and was a consistant complaint because most vehicles only came with a 12/12 warranty ( 12 months or 12,000 miles ) which regularly ended up being less than 6 months till the Japanese imports went 12/12 what ever came last .
Add to that the larger numbers of A10's in the UK comparred to OZ there is a much better chance of finding a good crank there, or Canada or US border states than here .

So yes some do big miles but there would be a lot more who do very little where as down here it is the other way round and the only chance of getting a good crank is a bike some one pulled down to restore 30 years ago then never got around to finishing it .

Last edited by BSA_WM20; 07/22/21 5:05 am.

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And because I can be just as narky

from the T140 Tyre Balance? thread on the British motorcycles in general forum

Post by Steve Jonesz

Quote
OK an update, missed the white spot on the VEE RUBBER tyre, I have now lined the white spot on the VEE RUBBER tyre with the valve and rebalanced, sorted, vibration gone, smooth at any speed! I contacted Avon and received an EMAIL back saying there tyres do not use a balance spot, they should work in any position, this was from the technical department. So I have a front Avon tyre which is four years old with about 200 miles on it, and it seems to be faulty as I could not get it to work in any position on the rim. Never fitted a VEE RUBBER tyre before but it seems to be grippy and stable, how it wears I shall find out in due coarse!

I think that works out to be 50 miles a year for whatever bike the Avon is fitted to .


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Hi Trevor

Think you should have started a new post, regarding the distance of your rides over the year etc. Rather than join this post which the topic was about engine power

My tuppence worth

John

Last edited by JER.Hill; 07/22/21 6:22 am. Reason: correction
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Actually the topic was about sourcing an A10 crank for a racebike engine build.

I did not come on here to start an internet fight.

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