Well, I'm saddened to say that my bike is in need of some serious surgery.

Late last fall, I had a countershaft seal leak develop - very small, I replaced the seal over the winter, it just looked like age and use had taken it's toll on it, While it was out I inspected the bearing behind it, all was nice and solid, no play whatsoever.

Obviously I was wrong, Sunday night, the entire bearing grenaded, the inner race shattered into a million pieces. Luckily, I was just upshifting to third, heard a strange sound, and immediately shut her down.

I don't think anything else is damaged, likely the back bearing on the shaft is almost toast too due to the 1/8th inch side to side movement I currently have on the front of the shaft - which would have transfered some torque forces to the rear shaft bearing as it was going.

I've been trying to figure out WHY this happened, the only thing I can see is September, when I bought the bike, the first thing I did before riding it was to loosen up the chain because it was relatively tight.

Anyways, damage is done, taking it to a shop is out of the question due to the costs I was quoted, so I guess I'm going to learn how to tear into the case - not that it's rocket science or anything, but it's one thing I haven't attempted yet..

My thought are to replace all 10 bearings while I'm in there, inspect everything else and zip it up again, check my piston, replace, re-ring as necessary, get my cylinder honed, new water pump shaft/seal as another safety precaution, my clutch feels good, so I'll likely leave it, re-shim my valves if needed and replace the timing chain.

Either way, I'm going to be done for for about 2-3 months to do this with the minimal tools and time I have available.

The only other economical alternative I could think of (to get me on a bike sooner) was to buy a 230 (CRF or TTR) and ride it for the summer, fix my bike over the winter, and give my wife the option of keeping the 230 over her 150 for next year and sell off whichever one she doesn't want.

however, convincing her to let me buy a temp bike (even for that scenario) won't be easy since she feels she'll have the 150 forever and wouldn't even entertain such a thought because women generally don't think that way.

Oh, and a quick question to the gurus, I phoned a few shops regarding repair costs (for a faster turnaround), one shop said that the output shaft is a known issue on a 2000 wr400f and yamaha had redesigned the part.

I thought I knew of every known issue with this bike, so was he just trying to sound smart?, sell me a new countershaft while at it?, etc.

Well, I've got it stripped down to the case, have to quickly throw together a home made case splitter tonight and I should be good to split it.

Everything looks A-OK so far, the screen type oil filter was pretty caked in shavings, but nothing got through to the top end.

Both shafts in the tranny have been superceeded with new part numbers - doesn't really mean anything has changed from a design/manufacturing standpoint, could just be an amalgamation of several identical years for ease of reference from a Yamaha DB standpoint.

Seem like all the remaining bearings are good, but I will change the rear bearing on the countershaft as well because IMO it took some lateral stresses when the front bearing failed.

Might replace the countershaft if it's scored at all since the inner chase of the bearing was shattered.

Top end all looked great, shims were typical factory standard according to the chart, so the valves aren't out much from factory, will reshim to large end of spec.

New rings & deglaze bore while I'm at it.


I would look at replacing ALL of the bearings as long as you are that far into it. You can pick them up at Motion Industries for a fraction of the cost of OEM.

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