Transmission won't turn after rebuild...

[Lanceam24]

Brand new here. Just recently got a 98 blaster that had no compressiOn. Took it after and discovered the piston ring shifted and kinda scratched the cylinder. Got everything torn apart, cleaned, and rebuilt. Everything goes on fine and seals up nice. But soon after the cases begin to seal the dang transmission locks up and will only rotate if I slip the sprocket on and use quite a bit of force. The crank rotates just fine it's just the trans. I'm sure it's in right I just don't know why.

I just rebuilt a yz125 from the ground up a few weeks ago and I'm rebuilding my yz250f engine at the moment so I'm pretty handy.

What would cause this? I'm thinking the cases might be warped, I guess a bearing could crooked or something. Just looking for opinions before I try and find new engine cases

 

[scotj77]

well you should have lapped the cases before assembly. and i would think you would notice a warped case when tightning them together. never heard of this particular problem though

 

[Lanceam24]

I may have fround the problem. The bearing for the transmission looks like its not fully seated in the case. When I tighten it the gear closest to the case must contact the outter race of the bearing thus causing it to not be able to spin. I guess i'll have to press the bearing in just a little bit further

 

[slickerthanyou]

I may have fround the problem. The bearing for the transmission looks like its not fully seated in the case. When I tighten it the gear closest to the case must contact the outter race of the bearing thus causing it to not be able to spin. I guess i'll have to press the bearing in just a little bit further

The bearings should not work themselves out. Should be a snug fit!

 

[Lanceam24]

yea but installing the new ones, i had to put the case halves in the oven. I didnt replace that one and I guess it sort of slid out a little. My yz125 even had a bearing fall out when I heated the case halves...

 

[scotj77]

yes this is very possible. I wold say that would be the problem. not much in the tranny that can bind, and warping is not an ez thing to do. i would fix that bearing and your problem should go away. I have had bearings fall out when the cases are hot. you should always pay close attention to make sure they are seated before assembly. and never assemble while still hot.

 

[Lanceam24]

I removed the seal and can actually see on the other side that its not seated all the way.

 

[slickerthanyou]

I removed the seal and can actually see on the other side that its not seated all the way.

Oh ok you heated it up it makes sense now!'

 

[Lanceam24]

Yup, just glad I found it. Just putting together this engine to have a little fun before I take a shot at installing this 465 engine!!