02 YZ250F problems

[Lee_533]

Ok, I've got an 02 yz250f that I'm about to sell because I'm done with it. Just did valves and rebuilt the carb yet runs like garbage. I can start it when it's cold, I can shut if off while it's warm and one kick starts it. However once it's been running and I shut it off and let it sit for an hour, it takes an act of god to get it to kick over. What am I missing? I'm literally posting the bike for sale tonight unless it figure this out because I'm overly pissed right now. Someone please help.

[Thommo_400f]

How does it run like garbage?

Low, mid, full throttle?

What symptoms, stutter, bog, dull, backfire etc?

Jetting?

More info and we can help

[jsjboss]

Carb adjustments. If you read through the forums there is much helpful information. I am very green to the yz250 my son just bought.Without allowing me time to look over the bike and learn he took it out when I left. Exploded the top end. I was ready to bail on it. As I read these posts these folks are a huge help. Don't give up. Check your jet numbers. They will even email you a complete manual. Hang with it

[morphrider]

Definitely sounds like jetting. How long have you owned the bike? A little history would help. 

[Lee_533]

I bought the bike off my friend who did the valves and I rebuilt the carb. I know the valves were done right because he does good work and we use to work on sportbikes together. I rebuilt the carb and did everything to specs. Before my buddy owned it we don't know the history. We got it off a kid who replaced the piston and a few other things but he couldn't get it to start, so we to the opportunity to get it cheap and fix it. The bike is very much rideable but if you try to just barely crack the throttle to putt around it jolts like it can't decide whether to accelerate or die. While accelerating it's fine unless you get on it from a low rpm, then it sputters like it's hesitating. At idle it's fine but if you throttle and chop it, it gets a lean backfire on decel. At idle if you try to throttle too fast it will kill it. And it's not because of the lack of oring mod, I know the yamahaa have a sea spot , this is worse. Basically if you try to take off you have to over rev the engine to make it go. Also, to start it cold, I have to tip the bike over to flood the bowl, hold it at half choke, and barely crack the throttle, then it will start. After that I can kill it and start it with one kick unless I let it sit for 30 min or so, then I spend 30 min kicking it until it starts or I get mad and just give up. Everything is stock on the bike other than an exhaust tip. When I rebuilt the carb I set the pilot jet at the stock setting, should I richen it up? Also, when I turn the idle air control out nothing happens, when I turn it in it dies. All the way out creates less of a lean back fire on decel. So should I try the pilot jet?

[morphrider]

This might help a bit..

https://www.thumpertalk.com/topic/258279-jetting-d-base-for-yzwr-250f/

[Lee_533]

Thanks for the link.  So I'm assuming I need to up my jet?  It seems most people on there were running a 185 main with a stock pilot.  And what's the difference between the blue and red needles?  I rebuilt my carb to stock, should I just go to a 185 main jet and 40 pilot jet to see how it reacts? 

[morphrider]

The red and blue needles they are talking about is a JDJet kit. It comes with 2 different needles depending on elevation. I picked up a kit for $50 off eBay and it seems super simple with rave reviews, I have just yet to ride. Throw that 185 in it and just play with it. It can be frustrating but in the long run will be well worth the hassle. Keep us posted.

[Lee_533]

Ok, thanks for the info. I'll have to give it a shot

[ronbuell]

Just a suggestion, check the float level before you start changing jetting.

[Lee_533]

Float level is set correctly . I adjusted it when I rebuilt the carb. Took it out in a ride today and it seemed to run perfect minus the decel pop. I think I'm going to get the oring mod kit and play with the jets.

[ronbuell]

Decel pop, backfiring, is normal to an extent. 

You could have an exhaust leak at the header/head junction; new gasket, or just alignment issue. 

You could also have a leak at the mid-pipe junction. 

You could try the next size larger pilot jet and adjust some, but others on here may weigh in on that.

 

Check FAQs, its probably in there.

[Lee_533]

Well it doesn't matter now because the bike is blown up. Must have jumped timing and just thrashed everything...so I guess I'm done dirtbiking for quite a while.