stock size jet on a 300ex

[WhiteBros400ex]

does any one know what size the stock jet on a 300ex is.

[WhiteBros400ex]

Dosent any one know the stock jet size on a 300ex.

[phebus]

Stock is a 122 Main, and a 38 Pilot.

[WhiteBros400ex]

Ok thankz because it is running lean and i need to up on the jet. I dont know why its running lean though because it is all stock but i guess i will change it to like a 125 and see what happens. Thanks man.

[cals400ex]

Originally posted by WhiteBros400ex
Ok thankz because it is running lean and i need to up on the jet. I dont know why its running lean though because it is all stock but i guess i will change it to like a 125 and see what happens. Thanks man.


how do you know it is running lean?

also, if it is running lean, how do you know it is the mainjet and not the jet needle or the pilot circuit? i don't think i would be going up on the main if your stock unless your in some mighty fine temperatures or at really low elevation levels.

[RedEX Baron]

my manual says a 122 is stock, but when i put my Dynojet kit in my stock main had 130 stamped on it, and im pretty sure noone ever messed with it, the bike was completely stock.

[WhiteBros400ex]

Its is tunning lean because the plug is white and idk why though because it is running stock. I am going to up the main jet be cause it is really cold out here liek freezing, and we have a pretty low elevation level.So i am going to up the main jet and see what happens.

[cals400ex]

yes, but your plug may be a whitish color for a couple reasons. your pilot jet is probally too small first off. i hear people running 42 pilots in their 300ex's instead of the stock 38's. also, the brand of fuel matters too. different additives give different readings. yes, in the winter months you should always go up on your jetting. jetting changes as the temp changes. i change my mainjet and needle setting about 3 times a year. the fuel skrew i probally change a lot more than that. do a plug chop and see if it is really your main jet that is lean.

by the way, the richer you go on jetting, the less power you will have.

[jerry-89-250R]

going up size won't hurt anything on a stock bike or atv, they are all lean from the factory too please the EPA

[cals400ex]

going up one size won't hurt the engine by any means, but you may have less power if the bike doesn't need it.

[WhiteBros400ex]

Ok ill do a plug check but i might up the main jet and run better fuel.The lower price gas these days is like freaking water lol.:)