Air Jet Adjustment- 2001 drz250

Ok, so far i have ground out the header pipe weld, larger exhaust tip, Twinair filter, two 1" holes in top of airbox, and DynoJet stage 2 jet kit.

after these mods the bikes now pulls like its possessed and now i really have to hold on throwing her through the trees :p

the only complaint is from idle to 1/8 throttle, it burbles and cuts out if i open the throttle all the way from a standing start (have to slowly open to 1/8), from 1/8 it runs fine (also starts and idles perfectly) so if i'm correct that puts my problem in the air jet circuit.

I've searched TT for air jet adjustment and come up more confused then i started, is there a tuning manual for the drz250? I've read that the shop manual isn't detailed enough and not worth the $70.

Any help learning how to adjust the air jets would be much appreciated



have you tried the air/fuel screw on the bottom of the carb? i turned mine out a few turns and it helped out my cold start issue i had. i still have the same exact off idle bog you have(i'm running stock jets but opened the stock exhaust tip and took off the snorkel) so i'm going to try and iron it out with the air/fuel screw. it's in an awkward place to try and reach with the carb sitting straight though. it's at the front part of the carb. little brass screw up in a hole that's pretty well hidden. if you know what you're looking for though it's not hard to find. if you need any more help i can try to get some pictures of it tomorrow.

I think air jets are a bit higher level then what you are chasing.

Its the Pilot jet, as milk said turning the pilto screw out will make idle a little richer, making it easier to start and providing more fuel just off idle.

But if it is idling and starting okyour pilot screw is probably about right, and you need to either change your pilot jet or the needle clip.

Or 1 final variable to confuse tthings more is that the pumper might not be working properly.

that makes sense, i don't believe it's the pilot screw because it starts just fine. (thanks for the offer milk, but i already found the screw. you were right it's pretty well hidden underneath)

Looks like I will be making a trip to the dealer for some pilot jets.

Last question is how does movement of the needle clip effect the carburetor? is it moving the clip down makes it leaner and up a position become richer?

aj here's some food for thought. what you're going to be addressing is the pilot circuit. since the problem lies from idle to about 1/8th throttle that is the pilot circuit. from 1/4 to 3/4 ish is the needle jet(which you usually don't need to worry with) and the needle position(clip) from 3/4 to wide open is where the main jet comes into play.

with that said, get yourself a mikuni #40 pilot jet and pop that in. This probably won't get rid of that off idle bog unfortunately though. It didn't for me but I definitely needed a step up on the pilot jet anyway as I had to turn my screw out past almost 3 turns. It's now just over 2 turns out and pulls TONS better on the bottom end. But I'm pretty sure the off idle bog we're experiencing is coming from the acc pump not being adjusted correctly. I'm going to take my carb apart once again and make sure it's squirting forward and have a look and see if there's anything noticeable wrong.

as for the needle clip, moving the clip up will make it leaner and moving the clip down on the needle will make it richer.

Let me know if you get your off idle ironed out.

oh i also have a thread in the jetting forum going about drz250 off idle bog...

thanks again milk

I will go grab a couple pilot jets and let you know how it ends up working out.

Please let me know when you tear down and adjust the accelerator pump i would love to eliminate the off idle bog

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