XR400 Jetting

I recently moved to Utah were im much higher than southern CA and will probably need to rejet. However... I know nothing about it, I will most likely ride between 5000' and 8000' ft. Is this something i can easily change with low carburator knowledge or will it have to go to a mechanic?

I say jump in and give it a shot. A manual wouldn't hurt but you can start with a stubby phillips screwdriver. Simply unscrew the 4 screws on the float bowl. Drop the float bowl. Turn off the gas cause it is now flowing everywhere....or turn off the gas to start with...your choice. There is a straight slot fitting on right side of the carb that lets you drain the bowl...this is even less messy....kind of keeps the boss happy.

After you drop the bowl down you will see a bronze hex type plug....this is the main jet....I think it is a 6mm socket... think.... take it out and look at the number you will probably want to go 3 or 4 numbers lower...buy several that are incrementally lower in number....smaller number smaller hole= less fuel. That is a good thing. The main jet affects the upper end of the power range.

The pilot jet is smaller in diameter than the main and is round with a straight slot opening facing down. It is about an inch long. Screw it out...look at the number and get some smaller ones as above. This jet affects starting and the lower end of the power band (usually a blue band).

After doing the above you will find you have a white plastic piece that you have no idea where it goes. My suggestion is put it in your pocket and keep it there. I have ran 2 xr-4's for thousands of miles and do not miss it. Zip it back up and ride on.

This is a very simplistic explanation from a simple mind. Hope it works for you.

Thanks for the info. I can't convince my dad that it can be easily done. :thumbsup: Also where can i buy new jets and do you have any recomendations as to what sizes for my altitude?

I'm in Wyoming. I ride between 4000 and 9000 with the majority of that being 6500 to 8000. A have a 416 kit in mine, the air box opened up, Uni filter, and an FMF Powercore exhaust. I run a 60/162 combo in mine.

If yours is stock you might try starting one smaller on each. Once you have the pilot jet at a happy medium, you can fine tune with the air/fuel screw. At that point if you need to adjust your main jet for elevation or temperature you don't need to drop the bowl to change it. You just undo the cap on the bottom of the bowl and you have access to the main jet right there. It's a snap.

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