The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Guy Wilson on 23.11. 2015 08:07
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Some of you were following my 'my small engine rattle' post that transpired was terminal big end failure on my '55 Gold flash. It had a small journal crank. My spare engine had a large journal crank. I can't see any obvious reason why they are not interchangeable and the large journal crank would fit in the original small journal crankcases.
Is this the case or am I missing something fundamental ?
Guy
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Hi Guy,
you are right. The crankcases are the same.
Only difference is the prefix showing whats inside. D is for big journals C for small.
cheers Klaus
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Thank you Klaus, I'll go the large journal route for now. I can't afford the replacement small journal con rods at the moment...
Guy
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The only problem I struck in doing that was the con rod nuts rubbed the cases. I shortened the nuts a mm and all was good.
Cheers
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Good to know!
thanks
Guy
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I have just made the same mod and I also had a probelem with the big end nuts catching on the cases. A couple of minutes with the Dremel to remove a mm or so from the inside of the case and all is well.
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So what the general consensus? Remove metal from the case or shorten the bolts? The bolts are surely cheaper to replace?
Guy
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I would put the crank into the case and see what happens first. I have fitted LJ cranks into early cases with no problems.