Gents,
When do you guys ever mess with the needle jet? I just bought FMF/power cores with boyesen reeds, reed spacer, K&N, and installed the 260 mains that were sent. I am at close to 6000 ft. in altitude and it is rich. I was told that all major jetting changes should be done with the needle jet first, then fine tune with mains. What do you KNOWLEDGABLE people say? I am going to be running with the airbox lid on, but with about 10 1 inch holes in it for the dunes..

RoostKing...

 

roost:

in my experience, it's the other way around. with the main jet supplying fuel at the upper half roughly of the rpm range, i would think the mains would provide the most significant jetting change opportunities. then fine tuning at the other rpm ranges could be accomplished by changing the height of the needle, needle jet number and pilot jet.

i have generally stayed with the pipe manufacturers jetting recommendations. if you are still rich, try a step down on the main...

 

Which part do you adjust to increase fuel on the low end?

 

on my two-stroke snowmobile, low rpm fuel delivery was increased by increasing the size of the pilot jet. i assume it's pretty close in an atv application...

 

-Air mixture screw for idle
-Pilot jet from idle to 1/4 throttle
-Jet needle for 1/4 to 3/4
-Main will effect from about 1/2 to full

Set the idle first so that it will idle fine. Next you need to set the main. To do this run it wide open if 5th gear for about 1/4 mile then pull in the clutch and shut off the engine and coast to a stop. Pull the plug and do a read. White way down inside is lean, black/oily is rich. What you are looking for is a coffee brown color. On a new plug it should be barely noticeble. If there is a wet ring you are going to be rich. Remember to read from way down inside not the nose of the plug. Now once you have that right set the needle. If bogs and misses like the choke is on at 1/2 throttle your rich. If you here it pinging or is weak at accelerating your lean. A nice long hill that you can climb at half throttle works good for this. You will know if your rich easily, lean you must listen to the motor closely.

No two quads are the same and must be jetted for max performance.

 

99BlueBlaster is right on..
You first need to set the pilot circuit/or idle.
The reason is this flow is always on, so it will slightly affect everything else you do.
Depending on where you live, and what kind of fuel you run. Reading plugs can be a little difficult. Im in the SF Bay Area and the fuel out here is junk and very hard to read on a plug...
I have found 3rd gear on a slight incline or hill. Bog the motor a little, then open the throttle all the way, Its a good test for checking a rich condition, if your rich it will bog pretty bad.
Hope this helps...