crank repair

[jimirobinson0]

Has anyone got experience of having a crank repair? I have spun the big end bearing on piston 4. I need to get it measured but I think once it has been reground to be even again it would be out of the tolerances.

thanks in advance

[amorti]

Unless they are in short supply (are you in USA?) surely it's time to replace the engine? Once you pay for the crank regrind, full set of main bearings, any gaskets you've had apart, etc. I think you'd be better off buying an engine off a breaker. You can still sell the starter, stator, covers, etc. off your broken engine or keep them as spares.

[jimirobinson0]

Thanks I have a spare engine. My question was regarding crank repair. The engines are race engines so are refreshed with the associated costs you have mentioned anyway. I asked the question so that I could gauge the cost involved against a second hand engine that would be refreshed anyway. If anyone has any experience I'd be interested.
Thanks

[L.Svedberg]

A common fix for broken shafts of any kind, and cranks in particular, is to have the damaged bearing surface ground free from damage, and then some 1,0mm more. Then you take the part to a reputable workshop with hot metal spray equipment to have it built up to some 1,0mm over the desired bearing surface diameter, then reground to spec.

This is a good method if you have the right contacts, if not a nightmare of trying to find the right places...

The other way is to leave the crank to a repair shop to have it welded up to oversize, then reground to spec. Both methods would also require the crank to be trued afterwards, and maybe even heat treated.

All in all, quite expensive stuff to do to an engine part readily available in good used nick for, say £50.

Good luck! /

Lasse

[jimirobinson0]

thanks Lasse

Good reply, I thought it wouldn't be an economical repair but good to hear someone else opinion. A few people on here have spare cranks so I'll probably rebuild the engine using another crank.

Thanks again