Yamaha XT350 puzzling main bearing prob

Right side main crank bearing fits perfectly in a steal outer ring. The outer ring seems to be cast into the right side case.

Problem: this ring rotates about 30 degree, back and forth, and moves up and down, in the direction of piston travel a total of 0.018". This is bad Right?

The engine runs great but has a tapping or banging noise. I bought this bike this way, my bad, it is a 96XT350 with 10Kmiles. It also needed piston, rings, pin, bore and valves lapped.

Can I replace the right side case only? If I only replace the right side, what would be the biggest problem; leak oil???? Will the tramsmission all fit together properly?

Has ANY one had a problem like this?

Wrong forum, but no, you can't replace one case at a time. The shaft bores are finish bored with the cases bolted together as a set ("line bored"). They can't be mixed.

Wrong forum, but no, you can't replace one case at a time. The shaft bores are finish bored with the cases bolted together as a set ("line bored"). They can't be mixed.

Thanks for the wisdom.

New to this thing. What Forum would be the right one. What is a Forum. :thumbsup:

The right forum for an XT350 would be the vintage forum, under Special Interest

This is the correct forum. It's a Yamaha Dual Sport. There are plenty of XT350 threads here. But correct, the cases have to be replaced as a set. Not sure if a machine shop could fix that moving "ring" for you, but it may be worth asking around.

Psycho

Not sure if a machine shop could fix that moving "ring" for you, but it may be worth asking around.

Psycho[/quote

It maybe possible for a machine shop to bore out the damaged ring and press a "repair sleeve " in it . definately worth asking around especially if you have it disassembled and can show them exactly what the problem is. quite possible that there may not be enough material left in the existing case to do that type of repair but you may not know until after the machining,If you are looking at cases anyway you will have to weigh the cost of a machining gamble against replacement cases.

i got a used casing on ebay for $100.00 last year when i needed one for mine. came with all the bearings in it. yamaha canada wanted $1500.00 for a new one with nothing in it. the ones i got had all good bearings but i replaced the seals for my peace of mind. broke out the timing chain guide mounts on mine when a cam bolt came out.

i would reccomend a new timing chain, guides and tensioner while you are at it as if it still has the origonal, it will be streched pretty bad.

Thanks for all the feedback. I asked a West Bay Machine shop if they had any way to bore the out of round hole round again. They said something like, not having a way to center it or hold it. This is the first main bearing, power side, that I have seen let alone worked on and the Yam shop really kinda himmed and hawwed about it also, just said to replace it. I have been able to determine that this ring has three radial ears or tabs on it which contains it between the inner wall and the outer wall of the case. It can not be replaced. My Boeing Engineering B in Law said that the forces applied to this power train would make half way repair only temporary, hense, I already tried the locktite and shims. So, I agree with all of you, I am on the ebay looking for used cases in good condition. Thanks for you help. I hope to be around a little more often. There are some good info being passed around on these threads and maybe i will be able to provide some help also. One idea I have is demo'ing how to make your own visor hyper opics insert using a piece of Lexan(polycorbonate) and 3M dble sticky tape. Best to you all.

RPM machine in Yarmouth, Mass can fix it they will bore the case out and install a new sleeve

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