jetting

I have a oo wr400 that i got in July of this year and up to the weather turning colder my stock jetting had been working good. However now it is running rough and after I ride for a little bit and turn it off it is hard to start and keep running. Once I do get it started again and manage to keep it running for a few minutes it seems to run Ok but everytime I turn it off I go through the same thing. The altitude I normally ride at is from 4000-7000 ft above sea level. Any help is greatly appreciated

[This message has been edited by GRC (edited 11-04-2000).]

GRC: It sounds like rich jetting. I'm assuming that when you say "it's running rough...", you mean it doesn't idle well and tends to stall if you let it try to idle. Try this, warm up the engine for at least 15 minutes and run it through the gears a couple of times, then set the idle high with the idle adjusting knob. Now, turn your fuel screw very slowly out(counterclock wise) and see if the engines runs even rougher. If it does, you have been too rich on the pilot ciruit. If it DOES run rougher when going richer, start turning the screw in(clockwise) until the engine runs smoothest and at it's highest idle(don't touch the idle knob while doing this). You may have to go back and forth with the fuel screw slightly a few times to find that spot, but when you do, that will be the best mixture for the pilot circuit and may correct the problem. Hope that helps. If you can't get it corrected by doing this, you may have to change your pilot jet size. The proper way is to go to a larger(richer) jet first and see it that makes it worse. If it does, then you go one size smaller than the first pilot jet you started with. The aim here is to always end up with the richest jetting that your engine will run well with because too lean of a jetting will melt pistons. :)

Your jetting is lean!! Cold weather leans jetting, It's common at the first cold weather enduro of the Fall for riders to seize (2 strokes anyway) on jetting that worked fine for the hotter weather. It's an old trick that when the temps drop you go to richer jetting (or pay the consequences). Good luck!

Yesterday was my first day back riding after having sinus surgery.What a great day!!!!. Thanks for your guys help in the jetting matter, found I was lean and had been that way since I got the bike. The spark plug had always looked pretty good though but I think that was because I would always idle the bowl dry before I put it away. What I thought was running good wasn't doing this machine justice. Problem was solved by going up 3 sizes on main jet, going to the 4th needle clip position, and backing out the fuel screw to 2 turns (it was less than 1 turn out). Seems like a miracle it would even run being that lean. It no longer pops when you let off of the trottle, from an idle you grab a hand full and there is no more hesitation, no hiccup just instant power. Thanks again for your help, See you in the desert

[This message has been edited by GRC (edited 11-04-2000).]

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