02 YZ250F Nuttin But Problems!

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02 YZ250F Nuttin But Problems!

Post by 4Strokes » Sat May 14, 2016 5:26 pm

Topic: 2002 YZ250F Nothing but problems!
Author: RideMx
Posted: 09/14/2004 11:47:32 AM

I know you guys probably seen my posts before about my bike not starting. Before it wouldnt start in the cold and that was fine with me, I figured i would re-jet it when it gets cold again. Now the bike won't start at all. I rode it about 4 times this summer and it ran fine all 4 times. I went to start it a couple weeks ago and i must of kicked 50 times and wouldnt start. I went and bought a new plug for it and that didnt work. I checked for spark and gas, it is getting both. This is my first 4 stroke and i am not familier with it, so if someone can give me some ideas i would really appreciate it.

Reply by Newby on 09/14/2004 5:27:29 PM
Humm, I cant say for certain what is going on with it but, have you tried spraying a small amount of brake cleaner in the carb and then kicking it over to see if it starts? If it does then you might just have a clog in the carb. If it doesnt start try a compression test. I know that is not what anyone wants to hear, but this happened to me on a bike I was fixing up. Got the thing to start ran it for a while then it refused to start again due to a valve spring failure.

Reply by fury469 on 09/15/2004 12:56:55 PM
how old of gas is in the tank try draining the carb bowl change the plug. and then try it.

Reply by SHea on 09/15/2004 5:17:55 PM
01 and o2 yz250f are notorious for not starting easily, so it's not just your bike, it's design flaws.

Reply by RideMx on 09/20/2004 10:04:24 PM
I basically tried everything. I was in the garage the whole weekend and accomplished nothing. I took the carb apart and cleaned it. I tried using starting fluid. I checked for spark numerous times. I checked the gap on the plug. I took my air filter out and tried starting it. I dont know what else i im able to do. I am thinking that it is an electrical problem and i hate trying to mess with wires. If anyone has seen or maybe knows what is wrong please let me know.

Reply by RideMx on 09/26/2004 7:52:16 PM
I looked at the bike this weekend. I got it started, but i had to push start it. Can't kickstart it no matter how long i let it run. After a few push starts and letting it run it lost just about all of the compression. So i thought for sure it was the top end. I took everything apart and the piston looked fine and the cyclinder was mint. I replaced the rings and kept the piston. Still doesnt run. It might need a new piston, but it doesnt seem like thats the problem. Any suggestions?

Reply by XR4DEZ on 09/26/2004 8:59:37 PM
Sounds like the compression release is open slightly. Maybe the cable is too tight. Valves can cause a problem with starting but not loss of compression.

Reply by RideMx on 09/27/2004 9:22:28 PM
I thought it might be the compression release. I will look at it and see if that works.

Reply by RideMx on 10/06/2004 12:27:45 PM
That was not the problem. I took the top end apart and replaced the rings and that did nothing. I took the head in to get looked at. Hopefully there is something wrong there because if its not that it has to be the cyclinder or the piston. If its neither i'm stumped.

Reply by Admin on 10/06/2004 12:35:45 PM
Low compression and ill-adjusted valves can both cause hard starting...

Reply by RideMx on 10/27/2004 10:25:42 PM
Now i am starting to get really mad. Just rebuilt the top end today. Still won't start. I had the head and cylinder looked at and i was told they were fine. WHAT IS WRONG WITH MY BIKE!

Reply by christlrmz on 10/27/2004 11:29:50 PM
My room mate has a 2002 yz250f as well. He had some problems as well with it starting so we bought the 2003 exhaust cam with the automatic decompression and it started a whole lot easier. We haven't had any problems with it since then. The only other thing I would suggest is to have you ignition module checked out you local dealer should be able to do it. I also have a shop manual for it I will look and see if I can find anything if so I will post it up as soon as possible.

Reply by RideMx on 10/28/2004 7:10:42 PM
Thanks for your advice. Unfortunatley i had to take it in because the season is almost over and im going to go crazy if i can't ride. Hopefully within the next few days it will be done. I will let everyone know what was wrong with it.

Reply by RideMx on 11/02/2004 12:30:11 PM
I just received the call today. Turns out i was missing valve schimes on the intake side and the rings were not expanding all the way. There are going to put the new rings in and schimes and I'll be up and running again. He said the valves and cyclinder look fine, so i saved a lot of money there. Thats what I was afraid of. I learned a lot about these 4 strokes from this experience and I hope i never have to do it again. Thanks for everyones help.

Reply by acguy on 11/23/2004 7:44:29 PM
Now go and buy the 03 exhaust cam, and have it installed. Throw away your decompression lever and cable after that. The bike will start like a XR100.

Reply by Barachie on 10/02/2008 5:06:35 PM
i bought my yzf250 used and it was breaking up as i rode it... we changed the jetting to fix the breaking up ( we believed it was because of the after market dr. d exhaust) and it fixed it however the bike was fouling plugs, and not starting... i took off my crab and cleaned it real well and now the bike runs like a champ.

Remember boys its not the machine that is junk, its the operator.
Man up.

Reply by wr250f95 on 10/02/2008 6:42:19 PM
Originally posted by SHea

01 and o2 yz250f are notorious for not starting easily, so it's not just your bike, it's design flaws.
its his bike, my 01 starts and purrs like a kitten very easily :)
are you using the correct procedure?
how are the valves? this bike is 7 years old, so it wouldnt suprise me if the valves were tight.

Reply by 250f canuck on 10/02/2008 7:07:50 PM
You do know this thread is 4 years old, right?

Reply by wr250f95 on 10/02/2008 8:40:08 PM
it popped up under active topics so i clicked on it?
im not complelty guilty, the guy above me posted 4 years later too :D

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