330ex jetting????????????????????

[tolson]

i need a starting point to jet this thing:
fst330kit, stock carb, port/polish, k&n, complete e-bros, mild web cam, race gas

any ideas on the air screw?
needle position?
main jet?

i just got it done. i have a 122,125,138,140 main jets. been messing with them and the needle position. no luck!!! BREAKS UP 1/2-FULL THROTTLE!

help:confused:

[dork]

does it break up with all those main jets? and is it like a lean bog or a rich stutter? are you running the air box lid?

remember with the bigger piston you'll have a stronger pulse at the jets, so you may not need to go much richer on the pilot, as long as the cam is not too wild.

[Mobile Dyno]

I just dyno tuned a 330ex with fmf Q-series full exhaust, cam, filter and we ended up with a 142 main jet and the needle in the 3rd position with the air/fuel screw out 3 turns. Depending on your location I would recommend a 140- 144 main jet and the needle in the 3rd notch and the air/fuel screw 2.5-3 turns out. Altitude has alot to do with jetting. Hope this helps. Let me know what happens. :)

[tolson]

all those jets broke up, about the same, less at the bigger jets. running stock lid. same through all the needle positions.
what are you saying about the pilot. 1/2 turn out or 3 1/2. further out the leaner?richer?
plugs arnt fouled.
seems lean and hot
bigger main?

[tolson]

thanks mobile dyno. i try 140, 3 turns , 3 slot and i'll be back in 15 minutes.

[tolson]

140 main, 3rd slot needle and 3 turn out. started up good and reved good, broke up a little at 3/4-full. rode it couple minutes, seems much better, then started breaking up at 1/2-3/4 throttle. pulled the plug, white. seems way lean.

anyone think putting the needle a 4or5 slot, richening it will help or do i need larger main jets? air screw-in or out?

[TRXRacer1]

If it's breaking up at 3/4-full then you need a bigger main. Go spend a couple bucks on bigger jets and see what happens. Your air screw won't help your top end at all. At 3/4-full your leaving to the needle and getting to the main jet mostly. All machines are different so only use others as a guide. Yours sounds like you need more jets. I'm assuming you don't have ignition problems.

[tolson]

what ignitions problems could i have?

[honda250xrider]

would try 4th clip down on the needle get yourself some 148-155 main jets and just test and tune i would say a 152 or so would be fairly accurate.