Author Topic: substituting a large journal crank for a small journal crank  (Read 514 times)

Offline Guy Wilson

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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

Online Klaus

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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


If you think, everything is under control, you are not fast enought.

Offline Guy Wilson

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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

Online muskrat

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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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Offline Guy Wilson

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Good to know!
thanks
Guy

Offline Dean

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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.
Never tell people your troubles. Half of them are not interested and the other half are glad you're getting what's coming to you.

Offline Guy Wilson

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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

Online trevinoz

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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.