[Jetting question on 300ex] - ATV Riders Forums - Honda, Yamaha, Suzuki, Kawasaki, Polaris, CanAm, Arctic Cat, Kymco ATVs

Pages:1

Jetting question on 300ex
(Click here to view the original thread with full colors/images)

Posted by: ssduane

Do the 300exs use the same small Mikuni Jets that LTZ/KFX use? I only want to pull the airbox lid and jet it for now and have extra jets from my KFX. And what would be a recommended size to go with for only lid off.

Posted by: bwamos

No they use keihin jets.

The older models use a long hex.
Newer models use short rounds (I beleive).

Even though they look similar.. they aren't compatible or on the same numbering system.

Stock pipe, stock filter, no airbox lid? try a 125 or 128 keihin jet.

If youre stock pipe & filter though. Just leave the lid on. You're aren't going to feel a difference with the restrictions already in place.

Posted by: ssduane

Thanks for the info. I do have a UNI filter for it and have noticed even with the stock filter and lid off it boggs a lot. I don't want to up the power to much yet, just a little so I (240lbs) can enjoy it a little more. Later it'll get more mods after my son (11) gets more experience and aggressive on it.

I'm really leaning to getting the Duncan pipe adn kit for it later down the road. I've all ready got a 14t sprocket for it and put my old 20" tires on it.

Posted by: bwamos

I'd use the 128 for the uni+no lid w/ stock pipe and header.
May need to raise the needle 1 slot.. but it's probably ok.

Slow circuit is probably ok until you change out the exhaust.

Posted by: ssduane

bwamos, thanks for the info, threw a 128 jet in t=it last weekend with the lid off and UNI filter on and opened the idle a 1/4 turn and she's a little stouter, plus with the 14t sprocket on.

Plan on taking it out the following weekend and test it.

BTW, my 05 had the tall jet.