The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: BSAmoto on 04.12. 2019 20:19
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Hello
As I just have an empty case (CA10R7967) I started trying alternatives so I put a Triumph crank in which seems to de do-able with a bit of work. Now I need the height of the 650 cylinder barrel between both gaskets. The 500cc barrel that I got has 87,5mm or 3,444". If the 650 barrel is same height I might need shorter rods so that measurement will let me decide which way to go.
Thanks in advance
Harty
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Isn't the Trihard a shorter stroke so you'd need longer rods with A10 barrel or a bored out A7 may do it ?
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Smaller big ends also.
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Yes, the Triumph is 82mm but I don´t care about losing a couple cc´s. Tomorrow I will offer up a Norton crank - if that could be made to go round with 89mm stroke that would be even better. Klaus came to the rescue and gave me the height of the 650 barrel. So now I have a number to work with.
Harty
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Isn't the Trihard a shorter stroke so you'd need longer rods with A10 barrel or a bored out A7 may do it ?
only 2mm
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Smaller big ends also.
but there wider
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Yes, the Triumph is 82mm but I don´t care about losing a couple cc´s. Tomorrow I will offer up a Norton crank - if that could be made to go round with 89mm stroke that would be even better. Klaus came to the rescue and gave me the height of the 650 barrel. So now I have a number to work with.
Harty
Norton rods are a lot shorter, may work with an A7 barrel
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I have put the Norton crank into the cases, it fits and cases can be bolted up. Of course the rods are now a bit shorter as the 650 Triumph rods but if al else fails I make a pair to suit. 89mm stroke sounds good!
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... if all else fails I make a pair to suit....
As a UK TV adverts says; Simples!
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GB..It's the pantomime season.....Simples....Oh no it isn't.
Without knowing what physical, mental and financial resources are to hand, this looks to be a project certainly out of my comfort zone, so if moto pulls it off it will be a well deserved world first. Me, I would sell the spurious parts and do a straightforward build. So good luck to moto, give it a shot. Maybe he is in the conrod business.
For our world wide audience, the character above is a puppet meerkat, Alexander, who encourages you to buy car insurance. The ads have run on UK TV channels for years, the strapline being" compare the market", but with his Russian Accent becomes "compare the meekat. Simple(s)"
"Buy insurance from a ****ing Russian Meerkat! What the **** is all that about?" Comedian Rich Hall again.
Swarfy.
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My well equipped workshop with all sorts of tooling machines makes tasks like this a lot easier as I could weld or braze all sorts of metal, grind or hone it to shape or machine it in any possible way. My prototype 905 Norton engine has homemade rods at 339 gr each, made from some swedish wonder steel, still 100 gr lighter as the std Norton rod - so almost everything is do-able. But so far it looks not too complicated as I would not need new rods. The Norton crank could be made to go round and the A7 barrel will happily fit on top the cases with a pair of 68mm Norton pistons - thus by coincidence I get 646cc! My measurements so far result in pistons at TDC protruding around a millimeter - this without any gaskets. So even compression should be okay for a touring bike...
Have to fit guides, seats and valves to a Norton head now but when that bike is out the shop I get back into BSA mode ;-)