Refresh of a 2001 Yamaha YZ250

Chasbo
Mar 18, 2020
10 min read

Updated: Apr 18, 2020

Another look back for me. I bought myself a YZ250 2 stroke dirt bike to do some trail riding here in Arizona back in 2015. It was pretty beat up, as most 15 year old trail bikes are, so I did a complete refresh. November 24, 2015

Just got back from checking it out and bought it on the spot. It is a 2001 according to the title, I have no reason to not believe that. It needs a few things. I have to replace fork seals/oil, put on a new chain and sprockets and replace a couple pieces of body work. The guy was in his thirties and had a list of everything he had done. It started on the first kick and rode nicely, although the shift into second is a little stiff. Other than that, it just needs a really good cleaning. He included a side stand, fresh rear tire, extra handlebars and the manual. The bike is ridden without being clapped out. I will ride it this season after doing those fixes and next season do a bigger tear down. Best part was not having to pay the asking price. He was prepared to move on the price. The bike had gobs of power. It sort of surprised me.

Started the tear down right away. I am greasing all the bearings and cleaning all the old grease and dirt off. I am ordering a fork seal and bushing kit along with a new rear sprocket and some body work. I might skip the rear shock until later this year. It isn't leaking yet.

November 25, 2015

Today I removed the bodywork, subframe and fuel tank to start to get at the layers of old dirt and oil. As I go along I am listing problems I find. Here are some photos of the kind of crud I am finding...

After first wash and disassembly

After the wash...

So far my list of immediate repairs includes

1.Fork Seals

2.Spark Arrestor

3.Front wheel bearings

4.Chain and Sprockets

5.Fix loose Shifter

6.Replace rear tire

7.Re-jet and clean carb

8.replace broken body work

November 27, 2015

I ordered my first round of replacement/repair parts today. That will give me a few more days to work on cleaning this thing off. I am only doing the most necessary stuff at first, those things that will get me out on the trails. That way I can spend a couple weeks riding it and decide how far I want to go with this build. Plus, once the bike is clean, I will see if there are any leaks or issues once I start riding it and can fix them then. So a spark arrestor, chain and sprockets, exhaust springs/o-rings and gaskets, skid plate, grips and shifter will get me rolling. In a couple of weeks, I am going to rebuild the forks with new bushings/seals and springs and then turn to the rear shock. Hopefully I will be able to complete all the important stuff by the end of January. Then I should know the bike well enough to decide on upgrades. Of course, looking at some of the builds people here have done makes me want to tear this down to the frame and create a fire breathing monster, but I bought this as a cheap way to get onto the trails and do a couple local race series, so just what is necessary right now and no more.

December 3, 2015

Made a lot of progress in the last couple of days.

First, lots of parts are showing up my front door. As I said before, at first only things I absolutely need. I will upgrade stuff later on when I have a better idea what I like and want to improve. So, lots of bearings, a new shifter, some new plastics, carb rebuild kit and such.

Second, I finally have finished the worst of the cleaning. Most of the caked on oil and dirt mix is off of the engine and frame. What is left I will take care of whenever I do a complete tear down. But I am happy enough with how clean it is now.

Anyhow, here are a few "after" pictures of the main part of the cleaning.

December 4, 2015

Today it was time to tackle the header pipe.

Before

After

I ran out of steam at the end. The work I did took about 90 mins. I got the inside of the pipe as well, where it mates with the crankcase and silencer. I dont think I will make it perfect. As far as I am concerned, at this point it looks one hundred percent better and it will be easier to track how much spooge I am getting.

At this point, the only thing left to rebuild are the forks and carb. I am waiting for the carb kit and once I get that done, I will get this back together and tagged so I can put my own dirt on it.

December 8, 2015

So I finally have EVERYTHING as clean as I feel like getting it at this point and have a final list of stuff I need to fix in order to be able to get out and ride.

1.Fenders, number plate and radiator shrouds

2.new grips

3.hand guards

4.sprockets and chain

5.front wheel bearings

6.exhaust gaskets and spark arrester

7.shift lever

8.carb rebuild kit

9.skid plate

10.fork rebuild kit

11.front brake pads

12.rear brake rotor

13.rear wheel

I found a decent used rear wheel to keep me going for now. I am going to rebuild my current hub up with an 18 inch wheel instead of welding it. Once I have ridden the bike for awhile, I will decide which jets the carb needs and I will slowly get to all the other needed stuff along the line. I want to get on the bike ASAP so I can figure out what needs refreshed and what I want to upgrade.

December 9, 2015

So today I got my carb cleaned up and rebuilt. Saw that it had the stock jets, which I won't change until I have ridden the bike a bit. I also got my rear axle adjusters cleaned up and anti-siezed. All I need now is for my new used wheel to show up along with a couple of other small parts and it will be time to finally get this YZ dirty.

December 10, 2015

Progress continues on the money pit. It is starting to resemble a YZ again. I got the header reinstalled and discovered that it doesn't fit square. I couldn't see that before because of all the baked on spooge and dirt, but I will need to address it I am sure. I am guessing that one of the previous owners went down on the left side and hit the header hard, bending it in the process. There is a good size ding there.

You can see that the pipe sits off the right side of the engine almost a 1/4 inch. It is flush on the left side.

That has to be the source of most of the crap that coated the header, engine and frame. Oh well.

December 12, 2015

So today I tackled my tweaked exhaust pipe. It was fairly bent and I didn't know if I would be able to fix it myself, but I decided to give it a try. I know Pacific Crest could fix it (thanks again for that tip Palmer), but if I was successful, I would save myself 70-80 dollars. Pacific Crest has a great DIY how to on their web site. Go here to see how it is done- https://www.piperepair.com/tips.htm .

Here is the gap before I started.

So I unbolted the pipe form the bike and put it in my trusty bench vise. The arrow in sharpie is a reference to show me the top center of the pipe.

Then measured the distance to a reference point so I would know when I got it right. I used a hammer as a pry bar so that the wooden handle wouldn't harm the pipe.

After nearly busting a gut, I felt the pipe give. You really have to push! The ruler showed I had moved it a quarter inch. Then I bolted the pipe back on and checked the progress.

The pipe is almost perfect now. The gap seems equal all the way around. So overall, I would recommend anyone do this fix if needed. All you need is a ruler, a bench vise and something to use as a pry bar. Plus, that is just like 80 dollars in my pocket and I will take that any day. Total time it took, including taking the pipe off the bike the first time, was less than an hour.

December 15, 2015

Today was both good and bad. That's become the norm with this bike I have discovered. Every time I make a little progress, I find something new to fix LOL. I got the tire on my new rear wheel (new USED that is). I went ahead and put on a new rim strip, rim lock and tube since the old ones were pretty much toast. The rear tire came with the bike, it has a couple of miles on it, but is in good enough condition to go ahead and run. Then it was a new Tusk brake rotor and JT 50 tooth sprocket. New bolts for both as well. I threw some 242 Loctite on the rotor bolts so they don't sneak out down the road. In fact, I am one of those guys that puts 242 on almost every bolt to keep them secure. After that, I put the wheel on the bike and liberally greased the axel while I was at it. Then I sized the chain and threw on the new front sprocket, a 14 tooth Moose Racing, with a new lock washer and got that all in place and torqued up proper. Then I threw the new MSR shifter on the bike, along with the front sprocket guard

The not so good came when I pulled the bike of my stand and found some oil on it. Crawling under the bike I saw that it could be coming from a couple of different spots. The clutch cover has been repaired with a little JB Weld, so it could be coming from that. There was some oil under the water pump and there might be a small leak there. The PO mentioned that the water pump was recently rebuilt. I am wondering how good a job was done. Plus, it looked like the CS seal and shifter seal were a bit moist, so they will need to be replaced at some point soon as well. I wiped everything of and put a fresh piece of cardboard under the engine and will check on things tomorrow to see where it is coming from. Stuff seems to constantly need to be added to my list, but at least the bike has TWO wheels back on it. That is a little visual progress, even if I will need to pull the front of when I do the fork seals and bushings.

December 17, 2015

Since it will be a bit before I get the new parts I need to finish my bike, I decided to clean the garage and take some pictures of my progress since it was nice and sunny.

There is the cracked clutch cover. There are a couple of repairs that have been done to it over the years. I am just going to get a new one with a fresh gasket. My skid plate will stop this from happening again I hope.

January 1, 2016

I got my new/used clutch cover in the other day, so I decided it was time to switch that out. First up, I installed the fuel tank and kicked it over for the first time in over a month. Took half a dozen kicks, but then it fired up no problem. It was acting like it was going to stall out, so I adjusted the throttle screw until it idled properly. Then I let it warm up a bit.

After it warmed up, I drained the old oil and sure enough, there was no drain bolt gasket. Once drained, I popped off the rear brake pedal and pulled the clutch cover. The gasket had a pinch in it, good thing I thought to order a new gasket.

The old clutch cover had a pretty good hole in it.

The new cover won't win any beauty awards, but then the whole bike looks well used, so it is a good match and at 30 dollars, was a good fit budget wise. I made sure it was torqued properly.

I also reinstalled the drain plug with a new gasket. I won't add oil until I replace the shift shaft seal and counter shaft seal.

January 13, 2016

So yesterday my final batch of parts showed up. Theoretically, I know can finally finish my little mule. So it was back to more disassembly and cleaning. I can now rebuild my front hub, the forks, shifter and counter shaft seals and some new plastic.

First things first, I popped the old shift seal out and it was a bugger to remove. It looks like it got painted at some point. A little work and off it finally came. Got the new one on real easy after cleaning the cavity and shaft. Then I installed the new shifter and adjusted the chain tension, installed the new rear fender and aligned the rear wheel.

Then I removed the front brake and laid it aside, followed by the front wheel and triples. At that point I spent some time cleaning the front end up and checking out the steering bearings, which I found were loose but well greased at least.

Before

Tomorrow I will rebuild the forks and maybe get to the front wheel bearings.

January 14, 2016

Got my forks rebuilt today. I only made one real bone headed mistake. When reassembling the second fork leg, I put the dust cap on upside down. I did the best I could not to mess it up taking it off and I have my fingers crossed that it isn't torn. Other than that, everything went smooth. The old oil wasn't too dirty, nice to see that the PO did refresh some things from time to time. It was obvious after rebuilding the forks that I will be going to stiffer springs. But they are nice and plush now.

Nice to have a bike stand for this job. It made the whole process super easy.

I also managed to get the bearings out of my front hub, but need to go get a socket the right size to pop them back in. So that will get finished up tomorrow. Now to just finish these last few details up and get to making it dirty again. LOL At least this time, it will be my dirt.

January 16, 2016

Well, it is finished for now. I worked all day yesterday until it got too dark to keep going and then finished everything up today. It started right up (after a dozen or so kicks!). There is still a bunch of stuff I need to do to it. It needs some new tires for sure, the ones on there are a bit worn, but I will get to that once I wear them completely out. This thing has a lot of snap to it. It is stupid easy to loft the front end. I guess that will take awhile to get used to.