help w/ my bro's '90 yz250 -tranny?

[pELYgroso]

so, I've had my brother's '90 yz250 in my garage for a couple years just sitting. The story is that we were going camping a couple years ago and brought bikes, and he didn't have one so I convinced him to get a cheap one and he could start riding with us. I found this bike on ksl, test drove it up and down the kid's gravel driveway and it ran great so I got it for my bro (he paid). As soon as we get it up into the mountains, it started to pop out of gear into neutral when hitting bumps. no matter what rpm or gear, it randomly would pop into neutral. This is obviously a problem if you're clutching around a corner up a hill. He had to park it all weekend. I called the kid (some 16 year old) as soon as we got back and explained the situation, and he had no idea about any problems.....riiiight. After trying to reason with him, he just denied any previous problems.

side note: I hate disrespectful jerk teens! I recently bought a bike back from a guy that I sold it to because it wasn't running right for him and I knew that it had acted up in the past now and then. It ended up being a loose cam chain that got more loose when hot and threw the timing off. Easy fix, but I took the responsibility.....end rant.

AAAANYWAYS, Is the popping out of gear something that could be a semi-easy fix? I parked it and haven't had time to tinker. I feel bad because my bro is technically out the $$ he spent on it. i'd like to fix it and either sell it and give him the money, or present it to him in some cool way that will surprise him...

Does anybody know these bikes?

Thanks in advance for your help!

 

[Rot Box]

Skip first paragraph if you don't like sorry time lol*

HAHA funny story! Anyone that knows me will say I have an unrelenting habit of talking crap on Yamaha's all day every day. When I was 12years old my friend and I saved up every dollar we had to pay our sh$tty local Honda/Yamaha shop to fix that exact problem on his 1990 YZ125. Back then I didn't know any better and after saving allowance and lawn job money all summer we paid them to "fix" it. Long story short and many hundreds of dollars later we took it out on its first ride since the repair.... Ever seen a clutch basket blow out of the side of a dirtbike engine and land on the ground before?! I HAVE! They screwed up the rebuild and told us to pound sand when we asked them to fix it. Yamaha's have sucked ever since lol

* On the shift cam there is a star wheel and a roller that sits in between the points of the star if that makes sense. As you push up or down on the shifter the star turns and the roller goes from one groove to the next and stays in place with spring tension (this is what shifts the gears and locks them in place). My thoughts are it is as simple as the spring being weak, improperly installed or a shot starwheel/roller/cam etc.

You are going to have to preform surgery to know for sure. Drain the coolant, drain the oil, pull the clutch cover and remove the entire clutch basket, hub, plates and pressure plate. To remove the large clutch retaining nut use an impact gun DO NOT use a screwdriver or pry bar to jam into the inner hub for leverage or it will break I will grantee it. Once you have all that out of the way you will be able to get a better look at the shifting mechanism. If all looks well and there is minimal wear and proper spring tension you could be looking at splitting the case to replace a bent shift fork or two...

Pulling it down that far is fairly easy however if it comes down to splitting the case you really need to figure out if it is worth the effort and money spent. If the bike is in decent shape by all means tear into it and post up if you need a hand it will be a fun project. That said if it is a ratted out, high hour, blown out suspension, weak topend-beater.... well I hate to see any bike get parted out and I have saved quite a few that should have been scrapped, but sometimes it is just a lot smarter especially with the price of used bikes nowadays. A Yamaha service manual is a must for a first timer (~$80), and a complete gasket kit, and new fluids are mandatory. If you end up splitting the case you will likely find lots of worn out parts especially in the top end. Transmission parts and internal pieces are not cheap either if you are lucky and they aren't discontinued :-\ If you do dive in be sure to keep everything CLEAN and organized you really don't want to loose anything

 

[jevyguy]

My dad had a KX500 that kicked out of 3rd gear down to second. We ended up replacing a bunch of the gears and that fixed the problem.

Does the bike pop out of every gear or just one gear?