thanx spike as usual your links were great

keep it coming guy's i think we need at least one place we can hammer this jetting stuff out
it get's old really fast jumping from forum to forum grabbing little bits of info

 

The biggest OEM main jet you can get is a #90 according to the service manual. Another bit of interesting info is that the 04 Polaris Youth ATVs are jetted and tested to operate at altitudes up to 12,000 feet. This is certainly the not the norm, mine suffers significant power loses at about 4,000 ft above sea level. After reading this I would think that an air filter and pipe would cause big jumps in the jetting numbers. The jetting is effected by thottle position not engine speed and if it is sputtering when you crack it open you may be able to help its reponse by moving the e clip on the needle in addition to going up on the main jet. Hope this helps

 

Here's a few cuts / pastes from another forum. Please verify before purchasing...

Note: Depending on location & other mods, jet 90, 120 & 13x seems to be the common jet sizes. It all depends on the altitude of the rider's location and other mods as well....

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I have installed both of the versions of Hetrick pipes on my boys 03 Pred. The version in the picture can be installed without removing the battery. The rear mount that you drilled out to bolt through the frame pipe is the side it should be on. It is a tight fit, but does fit perfectly. Did you buy the upgrade kit or just the pipe? The kit should include a 90 jet that seems to run great out here. I'm glad your happy with the pipe Rich and Michele have helped me out immensely.

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Big happenings tonight! I got the uni filter with the cover in the mail, got home from work with a fistful of spark plugs ready to work on jetting, slapped on the uni and new plug and yeeha! it took off like a rocket, I don't know why (bad plug?) but oh man! I ran it at half throttle for 2 minutes and checked the plug and it was a beutiful beer bottle brown, next I'll run it full throttle to check the main jet. I think Michelle sent me a 120 main (is that right?)

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Get an outerwear for it, be it the red foam one, or the fabric one. It will get caked with sand, but that is what it is supposed to do. The better way to go in sand is the "K&N RU 0200 with an outerwear", but you will be just fine with the UNI, that is what I run, it just gets real dirty after a weekend of riding. I run a 110 in the 50, so not surpewised to see 120 in the 90.

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Hope this helps...

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You forgot to richen the needle.