I rebuilt(more like restored) a friends 88250x. I was proud of my work when it was finished but very dissapointed to find that 1st gear wasnt working( it grinds alittle but goes nowhere). I was told the bottom end was OK but that was not the case. Has anyone ever taken apart a bottom end on one of these? I want to fix it and I have 2 parts engines but not much experience with bottom ends. Any help/advise will be appreciated

 

check and see what the the countershaft looks like. (its the shaft that the front sproket goes onto with 6 little teeth on it.) if there are no teeth or if there were worn enough it would just spin around the inside of the sproket and sound like its grinding.

BUT if all the other geard work than it is not this

 

I forgot to mention that 2nd -5th gears work fine, it actually runs very good.

 

Yes I've had several of those down to pieces. IMO, it's a straightforward and easy engine to work on. I also have lots of tran experience with that type constant mesh tran. Most likely a bent shift fork, the one that slides into first gear. You will easily see it when you look at it as a gouge on the rounded part of the fork. You should also replace the two gears that engage when this fork is moved as the dogs are no doubt rounded from grinding. This you will see also. Not a common deal and nearly always the sign of hard tran use, jamming gears without clutch and throttle let off. Or it may be possible to do this by jamming into first when the idle is very high. Anyway, the only special tool I can think of you will need is a flywheel puller, some other tools are nice for installing crankshaft but you can leave it in place. You will want a manual to refer to. The OE one is great. Scraping gaskets is the crappiest part of the job. Your parts engines should be handy about now.

 

I just rebuilt the engine to my 87 250x last year and I was having the same problem but with 3rd gear. All it was, was a fractured shift fork. It would shift into gear but not stay there. Shift forks run about $50 at the dealer, if you can do this yourself it is not that expensive of a fix. Good Luck[img]i/expressions/face-icon-small-smile.gif[/img]