Crank bearing spinning in case...

[CDBiker220]

So i posted before about crank end play on and 07 EC300. Turns out the right side ball bearing was loose in the case, and the crank. Causing the crank seal to leak. It slides right on and off the crank, and their is ridge on the bottom side of the case bore so it needed popped out with a hammer, but when in the bore it would spin. Would actually move in the bore up and down alittle and in and out. Clearance on the crank was zero and not loose. but slid on by hand. Should be an interference fit on both crank and case correct? Might just send the crank and case to RB Designs...from his website looks like he can handle this. The rod and piston bearings seamed like new, so I dont plan to rebuild the whole crank if i dont have too. All other bottom end bearings were perfect other than the sprocket output shaft bearing felt a bit tight, might replace it. Any advice other then talking to RB?

[GMP]

Thats the best plan. Sounds like a mfg tolerance problem on that case. Sorry to hear about that, not common. Good thing you checked, surprised it did not vibrate.

[CDBiker220]

It did vibrate a good bit more then my dads 2000 GG 250. But only a tad more then my yz250. So i figured it was just cuz it was a 300. Hopefully its ever smoother now. It will be nice to know that everything will be good in the bottom end when im done, plus now I know how to tear it down and how everything works. It didnt look like it spun much or anything, crank looks fine. It was raced in the 6 days....so it had a hard life...not surprised to find some problems.

[CDBiker220]

Well looks like RB will not be able to help me, apparently he does not have the material to fix a the bore for a bearing that size. Anyone know anyone else that does this kind of work I could talk too?

[hannesd]

does axial crank play always mean that the bearing is loose in the cases?
i do have some axial play, about 1mm orso...
mine does not really vibrate that much.

[GMP]

Axial means "in/out" on the line of the crank axis. Radial means "up/down" or "side to side" to the radius.

There is (or was) another place that can do that. I found it at one time but don't remember offhand. Time for some web footwork.

I suspect how Ron does it is machine a sleeve with the proper fit for the bearing as the ID, and bores the case for this to fit tightly on the OD. I also suspect he does it this way to avoid welding, but I'm not saying it can't be welded and rebored.