02 Yz250f Project

Just bought an 02 yz250f for 1300 today. Its my first 4t.

Was definitely beat up and has taken some falls. Was real hard to start but once it got going was good. Valves maybe?

Apparently it has all original engine parts. The engine has a lot of compression and makes no unusual noise when running or turning it over slowly. Thinking a top end rebuild is in order.

The suspension was lowered and sprung for 170lb rider by Pro-action in 05 and has a sticker to prove it. I actually like the lowered suspension a lot. Makes me feel more comfortable on the bike. So much smaller and lighter than my old 91 rm

The owner said it had not been started in 4 years until a few days earlier and by the looks of the bike I could believe that.

Should be a fun project getting this bike back up to speed.

I will update in a few weeks when I start ripping it apart.

Let me know what you think

This is what it looked like when I got it home.




Nice bike man!! Can't wait to see more pics. The trouble starting could be just from old gas and dirty carb but definitely check the valves

When I got mine, it would not start when the guy was showing it to me... I actually got it for a lower price because of that, too! Mine was just a matter of being freaking cold out, but I would:

Put fresh gas in the tank.

Pull the plug and clean it.

Pull the carb and clean it, mostly in the bowl area. Make sure all the jets are clear.

You'll also probably want to check the valve clearance and change the oil and filter.

Since you're used to smokers, remember that the oil needs to be changed every 5-10 hours, and the filter probably every other oil change. I got one of those Scott's re-usable ones and I'm real happy with it!

Also, when you start it, it's a little different. For mine, it will usually cold start with the choke on on the second kick, no throttle. Actually, if I push through one kick, it will always start on the first kick because that's the combustion stroke. Just remember not to use too much throttle when starting, the AP will flood it in no time! At most I use 1/4 throttle when it needs it but I come on it slowly so the AP doesn't flood it.

Since you got pre '03, you might want to swap out the cam for one of the newer ones with auto decomp. I'm pretty sure thumberfaqs has details on this.

You will LOVE this bike!

Okay I have read that the 02 is different than the 03. So does a stock 03 exhaust cam bolt right into an 02 making it auto decompression? I have seen hot cams but I want the most reliable option. It is real hard to start.

Are there other bolt on updates for the 02?


The frame and seat and airbox is a little different. The engine is the same. Stock 03 on to at leat 05 is a bolt in, just check your valve clearance before running it. Other bolt on updates, for what? Guts Racing or SDG seat, bark busters, skid plate, suspension revalve.....

I don't think I would rebuild the top end until I had a leak-down test run on it. If it's not making noises, has compression, runs good, and has low leak-down, its a waste of money and time. Run it like it is, then rebuild it.

You can use a stock 03+ exhaust cam or Hot Cams. No reliability issues at all as long as you check valve clearance

I don't think I would rebuild the top end until I had a leak-down test run on it.

Yea I was thinking don't fix it if it isn't broken but I was under the impression fresh top ends were more of an insurance thing on the 4ts.

Leak down test? How would I go about doing one of those?

I have the original service manual and I cant seem to find it in there

You probably won't find the test in the manual. You need to buy a test set which includes a hose that screws into your spark plug hole with a gauge on it. You hook it up to compressed air and it fills the cylinder with air and the gauge tells you how much air is leaking out. If it is leaking you can hear it come out like if you hear it in the radiator your head gasket is leaking. If you hear it from the oil fill cap your rings are leaking

Okay so I called the local shop and they want a 100 bucks to do the test. Seems pricey considering the price of a piston kit. I have an ancient air compressor that only gets up to about 50 psi so I don't even think I could do it myself even if I purchased the testing kit. Im thinking it would waste more money to get the test just to find out I need a rebuild anyway. Tell me what you think

And I think the previous owner may have updated the cam as I the bike does not have a hot start lever. Or he just took it off. When I get the head off I should be able to tell.

The front rim is bent, the rear fender is cracked, Grips are torn, huge dent in the exhaust can, clutch lever is broken, throttle sticks a lot, no missing bolts so far but a lot of loose ones. All little stuff in light of what I paid.

Im going to work on the bike tomorrow and wednesday and will snap some pics.

EDIT:Finally got a chance to try and kick the bike over myself today. Started first kick. They guy claimed that the gas was left on and it was a little flooded and that was why it was so hard to start and he was actually telling the truth. The idle is little rough and will cut out if you leave it at idle but i am hoping this is just a tuning issue. Even kicked over fine once it warmed up. Im so happy with this bike right now

Edited by snoboarder11592

Sounds like it just needs some TLC and she should be good2go!! If you can find an old compression tester you can adapt it to a make shift leak down test. It won't tell you how much is leaking but if it is leaking you can still listen to where it's leaking from. Use the part that screws into the spark plug hole but on the other end of the hose put on a nipple that you can hook your air compressor air hose onto it and just fill it with the air. 50psi should be more than adequate.

This is my first time actually ripping down a bike. A little overwhelming. I have been using baggies and a sharpie to label all my parts.

I got the front wheel off yesterday and plan on attempting to get the tire off today. I can already tell this is going to be hell getting the tire off and changing the bent rim.

Be sure and use a digital camera and take lots of pics. Make sure your wheel spacers go on the correct side and facing the correct way

A little lighter now. getting the motor out is todays project.

Bike was ridden in mostly sand. It sticks to grease pretty good. Once I get the bike to frame and forks I am just going to clean each part as I put it back together. Should Be a nice clean bike when I am finished.

Is there any way I can touch up the frame myself?

The spring was super loose to the point I could move it freely. There is some measurements on that pro action sticker. Do any of these relate to how tight this spring should be?

The rebuild will be slower and with lots of pics. Its really dirty, and needs some cleaning.



It's really tough to touch up a frame because getting an exact match is pretty hard to do then getting it to stick all of that and then it's going to wear out again. I've found some spray paint that was really close but not perfect. I touched up some high wear areas then put frame savers on. A lot of guys get powder coating done after stripping it down to the frame.

After a lot of debating I decided to rattle can the frame. I used VHT Chassis paint. Worked well and dries into a very hard finish. Also only cost about 8 bucks and I can touch it up when needed.

Also attempted painting my headers with the VHT Flameproof paint. Worked but I predict I will need to try again.

Purchased a cheap $60 graphics kit on ebay and a $60 number kit, and blue carb hoses on motosport. I also bought a new seat cover and new radiator hoses in blue on ebay.

Used bark busters off my old bike and added roost deflectors. The bark busters did not fit right but I made it work.

Overall I stripped the bike to the frame and replaced several spent bearings. I purchased a bolt kit because so many bolts were missing.

Took apart the carb and cleaned it out with carb cleaner. Was not very dirty like I expected. I hope to solve the rough idle with proper tuning.

Stay tuned for pictures. I will take one when the bike is finished.

I did not do a whole lot to the bike. Changed a lot of bearings, put some new paint on rusty parts, and threw some new stickers on. Im happy wit the result




Nice work!! Now go out and break it!

I did not do a whole lot to the bike. Changed a lot of bearings, put some new paint on rusty parts, and threw some new stickers on. Im happy wit the result




looks great man! :ride:

I dont know if your frame is painted or powder coated, anyways, you definitely want to cover up the sides of the frame because your boots will take the paint off immediately! if its powder coat, it will hold up better but it will still wear away. I suggest frame guards or buy come cloth tape like I used, it looks great!

Im not to concerned about the paint. It looks good now and I got my picture. If it starts rusting I will touch it up.

Im just glad Its finally in one piece and I can go ride it. I have not ridden since Sept 11 when I shattered my tib and fib, so needless to say, Im pumped for the weekend.

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