loose fit crank in bearing

[georgieboy]

Hi everybody,
For the second time my crank is loose at the bearing. I checked the side play with the cilinder off, and it won't touch the cases.
When i experienced it the first time i used loctite to fix the problem, but now after a few months riding it is loose again.
I have heard of go-karts running loose fitting on purpose so i want to leave it like this as i don't see it can become a problem.
Somebody any experience with above matter?

 

[yz125_894]

I was talking to eric the other day and he said that when that happens it wears everything else in the motor faster. also it may wear the plating and mess up the piston as it did on my yz125

 

[georgieboy]

Well, to think about it. The bigend got 0.8mm freeplay and that is no problem(it is even nessesary), now my crank has 0.5mm freeplay, where can it go wrong?? It is not touching anything, just freeplay.
I do know that they shim cranks of KTM's to keep the sideplay within specs.

 

[marcusgunby]

what happens is the crank will wear a groove in it,where it spins in the bearing, once this happens you need a new crank and bearings.You need the crank to be tight in the bearings and the clearance is in the bearing itself, a C3 bearing has more clearance than a C2 etc.

 

[georgieboy]

The crank is not spinning in the inner of the bearing. I checked for that. It is just a loose fit. I think i gonna split the cases and shim the bearing in a way that the axial play is within specs.
I revved the engine yesterday and you can see the flywheel moving axial in and out.
Well when you never check the play at the crank you won't even notice the axial play.
Bearings are still oke.
bi everybody and be carefull with the firework. I gonna teach my children how it is done. Dangerous job.