Have been reading posts and need help. have a 03 400i 4x4 manual, plug stays very black. i have a service manual for the 03's, it says my machine is jetted with a 150 main. have read posts saying a 145 is stock, i have not looked at mine. read a post where someone changed the needle setting from 5th position to 3rd position. are they talking about the jet needle. any advice on adjustments. also would like to have a tach. what kind will work, how do they work or install, and where can i get one.

 

By the looks of the fiche, that machine could have a 150, 147, 145, 142 or a 140 from the factory. If your 150 (you will have to look at the carb to be 100%) you could go 147 and be safe im sure. Your carb as stock does not have an adj needle.

 

I've got the same problem on my 98 454 that I just bought. I changed plugs when I bought it and checked it a few days later and it is soot black.

 

MtnRider, first of all what altitude are you at? You are right about your machine having a 150 mainjet. The set-up I use in the exact same machine is a 145 main jet with the fuel screw set at 1/2 to 3/4 of a turn out from fully screwed in. As for TnDuc check to see what main jet you have in it I think it is a 145. I would try a 140 main jet and set the fuel screw at 1/2 to 3/4 of a turn out. Try these set ups out and give us some feedback on how they work. By the way I ride at about 3500 up to 7000 feet and that set up i gave on the 03 400i auto works great.

 

Go to the www. highlifter.com site, they sell tachs for $139 or so. They're easy to hook up, just wrap the sensor wire around the plug wire a couple of times, and mount the tach with the supplied kit. I've heard of another company selling tachs, called sentrec or something, haven't been able to locate them yet though.

 

Listen to Snox314...... I put a 145 main in mine, and set the fuel screw at 1.5 turns out instead of 2.5 turns out. Run's great now......and and BTW, the needles are non-adjustable.

 

Who are you guys buying the jets from? I think I need to start a few mods after reading about simple mods making the a/c even better.

 

How can you tell if you need to rejet?? Just by watching your plugs or will performance be different? I just did the muffler mod on mine and looked at my plug and it is really black with a white tip on the electrode coming out of the plug. Mine is an 03 400i and I havent touched the fuel screw yet. I ride at 2-3000 ft.

 

Well according to dynojet when you call they say you cant tell by the plug anymore due to fuel additives. I dont know how true that is but people jet by plug for the last million years. Performance should increase. When i changed mine, there was a difference in 2nd gear performace on me old 98 with the 27in rubber. When i roll on the throttle its there faster and seems to pull harder before bogging down.

 

I agree, even though I am new to atv's I have been a motorcyclist for years. I have always jetted my bikes by the plugs along with seat-of-the-pants performance. Sure, unlimited access to a dyno would be great but for street (and now dirt?) riding it probably works just as good. I would just like to see what is the most common fix for my atv. Snox314, thanks for the recommendation. I am about 1100 feet elev if that makes a difference. Also, wouldn't your 03 400i and my 98 454 be carbbed differently from the factory?