2001 yz250 total rebuild

I got a 200 buck yz250 that supposedly only needed a piston. I found that it needed EVERYTHING. I've got a new cylinder, engine bearings, seals, and carb kit. I need new center cases because the previous owner was apparently a chimp with a hammer and couldn't do any repairs without destroying the cases. This will be long time rebuild thread, but I'm starting out with a few pics of what I'm dealing with. Literally every bolt broke during removal, so I'm going to be drilling out bolts til the second coming. I hope to be assembling he motor in a few weeks, so hopefully I'll have more meat to add to this post. If anyone has any parts or advice they can give or sell me, please feel free! Thanks!

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The crank had blown the main bearing, the power valve didn't have a seal on the rotating shaft, and the head was destroyed. I also bought a head for a 2000 model, but its good enough. I sold the old cylinder for 100 bucks on ebay, so the new cylinder only cost 259 bucks! As cheap as a replate, but much better for my piece of mind. I've got a bid for a complete set of cases on ebay, so I'm praying I get them so I can begin assembly. I found all the inner case bearings at a bearing supply house for a grand total of 25 bucks! They seem to be good quality for the low-stress areas such as water pump amd power valve. I'm going yamaha for the crank bearings and seals, though.

My jaw dropped so hard when I saw the picture of that head... wowwwwwww

All the best with the rebuild

The new head looks awesome, though. It's polished and lapped like a shiny diamond:) I desperately need new cases though, and I hope somebody can help me out. I've got a fever, and the only prescription is to ride this yz250. :)

Seem's to be we're both in the same leaky boat! :rolleyes: I'm in the midst of completely rebuilding my '01, have yet to spit the cases. It'll be my first time ever doing so, so I may be coming to you for some help haha.

Why replace the head? That's the latest and greatest version of the Singh squish grooves to promote turbulance. :D

Good luck. At least the price was right and you knew something was up. I feel bad for the posts where someone paid good money of a "fresh" bike to find it has 4.2 trillion hours on it and 3 pounds of sand in the motor.

Why replace the head? That's the latest and greatest version of the Singh squish grooves to promote turbulance. :D

Good luck. At least the price was right and you knew something was up. I feel bad for the posts where someone paid good money of a "fresh" bike to find it has 4.2 trillion hours on it and 3 pounds of sand in the motor.

The funny part is, the day before, it ran and I told him I'd give him 1000 bucks for it. The day I was to buy it it blew up. I should've offered him 100 bucks, but I figured I could part it out for quite a bit more than 200 bucks. It's going to be a long slog, because my truck is down for repairs and I can't take any parts to be welded, painted, etc. I figure by Christmas it'll be done. The motor will be like new, with almost every part new. The frame is to be painted by a friend who owns an auto body shop(for free!). I'm thinking white plastic with a sea foam green frame and seat cover like the early 90s ktms, or red frame with white plastic and retro 1986 yamaha yz graphics. It's going to be a long slog just to sandblast and clean the parts, plus removing the old bearings from the swingarm and links. I've got nothing but time, though.

Still a pretty good deal IMO. Wish I could find a project bike like that.

Seem's to be we're both in the same leaky boat! :rolleyes: I'm in the midst of completely rebuilding my '01, have yet to spit the cases. It'll be my first time ever doing so, so I may be coming to you for some help haha.

feel free! I'm almost an expert on the internals now :) believe it or not, I've not fooled with any bikes since I had a 1986 rm250 that I stripped and rebuilt in 1990. I never forgot my mechanic chops, though- but I had to ask a few dumb questions on other forums when I first got the bike because I wasn't familiar with some of the new tech. That old rm 250 had 36 horsepower(like a 125 of today!) so I'm real anxious to feel what 44 horsepower feels like! I plan on port matching the cases, putting on a stock pipe and replacing reeds when I'm done. Nothing too extreme. I'm either going to keep this and pass it down to my youngest son, or trade it out for a good rm250 if I can find one. I'm a suzuki man to the bone to tell the truth. Odds are good I'll be keeping this one. Be patient, because if I can't find a good set of used cases, I'm parting it out- and you might get some killer deals on brand new engine parts!

Still a pretty good deal IMO. Wish I could find a project bike like that.

id have been golden if the cases hadn't been shot. That's an extra layer or bs I hadn't budgeted for.

id have been golden if the cases hadn't been shot. That's an extra layer or bs I hadn't budgeted for.

Yea I just noticed that... I missed it the first time through. That blows man!

$120 seems to be the average price for a per case side. So you're looking at $250 for new cases. Unless some pop up for a better deal.

Edited by BDubb106
feel free! I'm almost an expert on the internals now :) believe it or not, I've not fooled with any bikes since I had a 1986 rm250 that I stripped and rebuilt in 1990. I never forgot my mechanic chops, though- but I had to ask a few dumb questions on other forums when I first got the bike because I wasn't familiar with some of the new tech. That old rm 250 had 36 horsepower(like a 125 of today!) so I'm real anxious to feel what 44 horsepower feels like! I plan on port matching the cases, putting on a stock pipe and replacing reeds when I'm done. Nothing too extreme. I'm either going to keep this and pass it down to my youngest son, or trade it out for a good rm250 if I can find one. I'm a suzuki man to the bone to tell the truth. Odds are good I'll be keeping this one. Be patient, because if I can't find a good set of used cases, I'm parting it out- and you might get some killer deals on brand new engine parts!

Dang a whole 36hp?! :p Its a lot more satisfying to have a bike you put countless hours into making, I really enjoy all the work (just not coughing up all the dough...). But thats pretty cool, I think your son would appreciate it more than if you went and got him a new bike. And if you do end up parting it out I call first dibs!! :p

Here's some more pics. Broken motor mount, seized bolts, and destroyed bearings plus crank with shot bearings . :)

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Edited by Rancher420

Yea I just noticed that... I missed it the first time through. That blows man!

$120 seems to be the average price for a per case side. So you're looking at $250 for new cases. Unless some pop up for a better deal.

problem is that the left hand side case is as rare on ebay as hens teeth. I can find a million right side cases. That left side case is going to be the difference between finishing the build or selling the parts cheap. Edited by Rancher420

Dang a whole 36hp?! :p Its a lot more satisfying to have a bike you put countless hours into making, I really enjoy all the work (just not coughing up all the dough...). But thats pretty cool, I think your son would appreciate it more than if you went and got him a new bike. And if you do end up parting it out I call first dibs!! :p

i can still remember how that bike ran to this day! It was a good old ride, with decent suspension. I actually ported it myself, and keyhole bored the carb with a Dremel- and surprisingly it made noticibly more power! I can't believe that I was brave enough to do stuff like that at that young of an age. Now, I'm all about reliability and keeping it stock as possible. 20 odd years and five back surgeries will ensure that I don't need need more power!

problem is that the left hand side case is as rare on ebay as hens teeth. I can find a million right side cases. That left side case is going to be the difference between finishing the build or selling the parts cheap.

Yep that is always the one that gets trashed!

I'd like some color scheme ideas if anybody had any.

For the entire bike or the motor?

I'm thinking this but with a green frameimage.jpg

I'm thinking this but with a green frameimage.jpg

That would be sick... Im a fan of odd colors and one of a kind bikes.

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