250R crank locked up after putting the cases back together

[HondaATC500X]

Alright this is really about to drive me nuts. I had a center case gasket blow out between the crankcase and counter balancer chamber and I tore it down to replace it. During the disassembly, the right side main bearing came out of the case and stayed on the end of the crankshaft. It was not solid though and still turned fine. The left side however had pushed through the main bearing enough tht it was dragging the case. I had gotten it back into position where it would turn freely before re-assembly. As I was putting the case back on I had a pretty difficult time getting the case to go back over the main bearing and in retrospect I should have tried removing the bearing and installing it directly into the case like normal but I didn't think it was really going to hurt much. After getting the case back down flush and into place I realized the crank had locked up again. I checked the spacing in between the crank weights and the side of the case on each side and found the left side was almost slam up against, and the right side had a nice gap. So I worked on tapping the left side of the crank back over to where things are mostly centered. I've checked each side with a feeler gauge now and have .025 or as close to that as I can get between the crank and case on each side but its still tight as hell.

Something I did discover it feels like when I'm running the feeler gauge down the sides that I'm catching on a very small edge of the main, on both sides. I'm running a hotrod crankshaft, and heres what I'm speculating happened. The tolerances on the hot rods crank are making the bearing fit on it a little tighter then normal and the bearings have actually went onto the crank far enough that they are not table to seat in the case properly and its therefore allowing the crank to rub on the inside of the crankcase on the sides. The only thing that really screws me up I don't understand is the fact that when I turn the crank with a wrench on the flywheel nut, it has harder, and softer parts in the rotation. Still no where near as free as it should be though. Any insight or ideas on this?

Figures I would hook my last center case gasket down with a more then generous amount of 3M super weatherstrip adhesive before this happened :rolleyes:

[matt250r21]

Just throwing this out there, Is you crank out of balance? I droped one of my Honda cranks on a tile floor and it throw it out of balance. Just for the hell of it I tried to put it in a back up motor to see how bad it was and it was catching on the aluminum of the cases. Kinda sounds like what your hot rod rank is doing at the end of your post.

[HondaATC500X]

Maybe...I bought it brand new though and its got less then 5 hours on it. Doesn't mean its not possible though. At this time I'm going with the theory that the main bearings are not going into the case halves straight. I guess I gotta rip it apart again.

[C-LEIGH RACING]

Originally posted by HondaATC500X
Maybe...I bought it brand new though and its got less then 5 hours on it. Doesn't mean its not possible though. At this time I'm going with the theory that the main bearings are not going into the case halves straight. I guess I gotta rip it apart again.

Thats more than likely it.
When you pressed the crank into the left side case it put the bearing in a bind & didnt go all the way in. Now with the cases together & by the left side bearing being not completely in, it binding the crank inbetween the bearings. Loosen the case bolt & pry the case apart some & see if the crank will turn then. If it does you know what the problem is.
Another thing, when you press in a bearing you put side load on the races & balls & thats not good on the bearings even though they are big.
Heat the case & put the bearing in the fridge & while the bearing is cold, it will drop right into place in the case.
Then heat the bearing & put the crank in the fridge, then do it just like you did the bearing.
It will be so easy installing the bearings & crank like this you will think you done something wrong.
With an oem crank & bearings, the crank is a tight fit in the flywheel side bearing but the clutch side of the crank is a slide in fit into the bearing.
Neil

[HondaATC500X]

Thanks for the reply C-LEIGH. I'll try and get motivated to tear into this thing again and I'll go about putting the bearings and crank in like you mentioned.