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Hi everyone, I want to do the airbox mods and uncork the exhaust as per many posts, I have ordered the JD Jetting kit, but will take a couple of weeks to be shipped here, does anyone have any guidelines on what stock jet sizes to use until my kit arrives?

I ride at approx 6000ft bout 70F and occasionaly ride at sea level.

Awesome site, lots of usefull info.

Thanks
Ben

Hi Ben, I'm in the same boat as you almost.

Just bought an '08 250x, and I run it mainly around sea level and from 40 - 70F.

I'm doing the airbox cutout, air filter screen, and drilling the exhaust. Then rejetting with a JD kit.

The instructions say red needle, 5th clip, and 160 - 165 main jet. Pilot doesn't need changing on '07s and '08s apparently.

Let me know how you get on, and I'll keep you posted.

Lance

I would go with the 155 main 42 pilot and red on the 4th.

With the 150 it is perfect at my normal riding area but I am afraid it would be too lean the few times I ride at lower elevations, It ran good at both with the 155

Runs crisp with o bog.

Year: 2004
Elevation: 4,000 - 9,000
Temperature Range: 50 - 100
Smog (AIS): No
Airbox Modified Top: Yes
Airbox Modified Sides: No
Backfire Screen: Yes
Air Filter: Stock
Pilot Jet: 42
Main Jet: 155 now 150
Needle: Red
Needle Clip Position: 4th
Fuel Screw Type: CRF's Only
Fuel Screw Setting: 1 3/4 now 1 1/2
AP Modified: No
Leak Jet: 55
AP Cover: No
Exhaust Type: Stock
Exhaust Modified: Drilled
Pink Wire Modified: Yes

If you look at other 250X posts on here, you'll find some very similar suggestions.