[CALVIN]

I am new to jetting and while I understand the basic concept I don't know how to troubleshoot. I bought a JD Jet Kit for a 2007 250X I bought. The previous owner installed a QS2 that leaked slowly when the gas was on. After too many hours, & lots of web surfing I was able to pull the carb. One of the O-rings was pinched in half, so I bought the whole kit to replace it. I got the bright idea to re-jet since the carb was out. Went to the 160 main & 42 pilot with the red needle on the 4 position. After market fuel screw is 1.5 turns out. Zero to half throttle it has a lot of go. After that it bogs & misses . Plug is pretty black, so overall I must be running rich...right? Is the next step to go to a smaller main jet? 155 or 158 or might it be another issue? Any thoughts appreciated.

THANKS!

[Leardriver]

You are on the right track.

You don't have to remove the carb to re-jet, but if you already have it out, it makes it very simple.

Try a 155 main jet if you have the top of the airbox cut open. If not, you should open it.

A 42 pilot is fine, but at 2.0 turns out on the fuel screw. Your bog is probably related to needle clip position. Try the fifth clip from the top, especially during cooler weather.

That change, along with more fuel from a richer fuel screw position, should make a big difference.

[CALVIN]

Thanks. Airbox is open. I should olny make one change ate a time (main jet first)...right?

[Leardriver]

I spent a lot of time on the '06, which seemed to be the boggiest. Is that even a word?

Anyway, those settings I recommend work fantastic, so you can feel comfortable making those little changed all at once. The main jet won't affect your bog anyway.

It feels like a weak accel pump, but it is really a lean pilot combined with an even leaner needle on the stock needle.
If you go to an R cam or a Hotcams stage one, both of which are awesome, you may even need a 45 pilot.

[CALVIN]

Thanks again for the advice. keep in mind I am new to this s you read my follow up questions.

I understand going to a smaller main jet if I am rich above half throttle, but raising the needle jet another notch allows more fuel through the carb...right? Is there a chance it will still be rich above half throttle?

You mentioned that a weak accelerator pump may be the problem. When I replaced the crushed O-ring on the QS2 cover I also swapped out the diaphragm. What would make it "weak". I am a little fuzzy on it's purpose. I thought it was for the initial throttle hit.

Finally, "bog" may not be the right word. Above half throttle it seems to almost choke out & the RPMs seem to flatten out.

Again any input is appreciated. I think jetting has frustrated much better mechanics than me.