250R crank locked up after putting the cases back together

[Billy Golightly]

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 dissasembly, 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 realised the crank had locked up again. I checked the spacing inbetween the crankweights 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 :lol:

[ColeTrickle]

I've put cases together before and got the main bearings a little crooked in the cases and experianced the "tight spot" your talking about. I figured it would loosen up once I ran it a bit. (like they often do) The bike started and ran but didn't sound quite right. I ran it longer and the mains self distructed. I took it all back apart ond put OEM bearings in it straight. I had used ALLBALLZ bearings. At first I thought it was junk bearings but after thinking about it I just had the mains too crooked. I bet your main that stayed on the crank might not be straight enough. I also always take the mains of the crank if they stick, sometimes they can be very difficult to get off. Twice on bikes that blew a crank seal and toasted the bearing I had to cut it off with torches. I have'nt run into rods not being close enough in size that they were causing a clearance problem but you never know! Hope that helps, Drac.

P.S. when pressing mains in properly you push against the outer race. Putting it together with the main on the crank puts all the force on the inner race, already ruining it.

[Billy Golightly]

Well that doesnt sound re-assuring at all :lol: I was figuring I'd have to split it again (and scrape the gasket surface, again)

[ColeTrickle]

Yup, I never use sealant on centercase gaskets because you might have to take it apart and no re-using that baby. Yama-honda-kawi-bond is the best. Use that with out gasket or a little bit with your gasket if you're scared it will leak. That stuff cleans off the cases better too..

[Billy Golightly]

Thats what I did last time and I had the gasket blow out...so I was determined (a little to much) to make sure I didn't have a repeat this time. Looks like I'm gonna have to pry it back apart and try and get the mains off

[madmanwithmouse]

give the crank a good soild smack with the end of a 6x6 piece of wood from both directions. act like you almost want to knock it out of the case. do make sure the nut is on anywhere there are outer threads tho.