This problem is blowing my mind.

Ha~Ha….It’s fast, but I don’t think that’s the issue. I’ll keep the kit…..
Not sure what it could be yet.
I split the cases over the winter because I got some crazy idea in my head that I had to re-build a bike that had almost no hours on it simply because I purchased it used as well as I though it vibrated too much.
I replaced most bearings and all seals and it has run flawless since the rebuild.
On my parade lap around BC Sunday I stuck a nasty rut pretty good and it started to shift funny after that.
I didn’t make another full lap before it was stuck in top gear.


 
You guys sound like a bunch of doctors standing over a patient that they have no idea what's going on but a little inclination. And Marc is like the top dog doctor who took charge and spit out what the problem probably really was....
It sounds like maybe the drive dogs on either 3[SUP]rd[/SUP] or 4[SUP]th[/SUP] gear have started to round a little allowing 5[SUP]th[/SUP] to slip out.
Click to expand...

Maybe with 20 years more experience I can diagnose bikes that well.
 
Well, I took it all apart last night and even though the shift drum was still locked up after disassembly, I found nothing unusual.
I flipped the case over to remove the countershaft nut to be able to extract the transmission….and after impacting the nut loose it miraculously started shifting again !!!!
I’ll look closer tonight…
 
Yeah.......:p....that and a few other big nuts I probably shouldn't have...Ha!<O:p</O:p
I’m starting to think it was just jammed up from too much pressure on all the s**t I impacted. <O:p</O:p
I surfaced the cases when I had it apart over the winter taking off a few thou on each side. <O:p</O:p
That maybe coupled with the overly tight counter-shaft nut may have bound things up????<O:p</O:p
From now on, the big nuts are going to be put down with a torque wrench.<O:p</O:p
 
I was curious, wondering if I should be impacting mine when installing.

I've had to use the impact to remove a couple before, but always just used torque wrench when re-installing. I always figured that it has the keeper washer to keep it from turning off if it were to work a little loose.

While mowing my grass (at 9:00 oclock last night) the thought occured to me, the impact that the counter shaft endures just from the action of the rear wheel chained to it "has to be as severe as you would get from an impact wrench"?

Knock on wood, my 2003 YZ250 has been a fantastic bike for me. Super Reliable. I don't see myself ever getting rid of it.
 
I have been using an impact on the counter shaft sprocket for all 30 years of my riding career....never have had an issue. Mind you I dont give it everything the impact has either.

Also when tightening the nut you are only squeezing the sprocket against the spacer that bottoms against the main shaft. It is not going to effect the clearance between the cases on the main shaft.
 
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