leak jet mod

ok ok ok, I've been searching for about 2 hours now and I'm right back where i started! :D:D How about sum straight answers people? maybe a sticky thread? There are ton of forums about the 450 lj but my bike has a # 90 lj not a number 70. Thanks in advance! :D

There's a crap load of good threads about this if you search. First of all what bike do you have?

Most likely the answer you'll get is a #40 leak jet and tune your a/p.

I have a 2004 250f. I did look through a ton of those threads and came up with nothing that helped me just a headache! :D

I live in Pa. (Poconos) and the 40 leak jet was the ticket for me. Should be the same for an 04 Yz. Order one from the dealer but you'll probably need the part number. I think I have it somewhere and will post back.

what was your stock leak jet though?

i might be mistaken but i think the wr's is smaller?

Pretty sure it was a 90 also.

Where in Pa. are you?

Here is the link for part numbers:


A 40 would be 4JT-1494F-03-00

While searching I read a post that the Yz carb doesn't have a leak jet!? I'm pretty sure (99%) that is wrong. Never heard that before.

I have an 02 WR 250, got the JD kit and had bad bog. Got on here and read allot. Bought a 40 leak jet...still a bog...loooked into the AP timing thing...

Well I kept reading how you need to time the AP to just miss the slide...when I adjusted it all it did was make the squirt longer or shorter. Tried to make it go about 1 second and seems to have made it good...I still don't understand, cuz I always read it times it, not makes longer or shorter...yet tried it cuz tired of bog...seems to of worked for me :D :D

I had a 107 leak jet and I'm at about 100 feet above sea level. I popped a 40 leak jet in and no bog problems.

A little off topic, but did you guys have to go in with your fuel screw or make other adjsutments? I think mine is running a bit rich.

I'm a little south of Pittsburgh. What I don't get is how people in different elevations can use the same leak jet? I thought elevation was one of the factors for jetting?

I don't think that elevation would affect the overall function of the leak jet that much but could be wrong.

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