300EX Jetting

[StupidHurts]

My freind asked me to clean the carb on his 300 and as i took it apart and got to the jets i saw that the Main jet was a 118 and the slow jet was factory...
It has a Curtis Sparks X3 on it
K&N Filter with outer ware
No air box lid
The last owner said he put a Curtis sparks jet kit in
But i was wondering what size the jets sould be??
It seems like it runs way to lean and it over heats pretty quick..
The pipe is cooking after 10 min of riding
Even in the winter..

???
Should these jetts be bigger then 118 and factory??

Thanks

[gixir]

I just put a hmf on and they recommend a 125 main(my 300's stock). 118 seems to small to me.

[JohnT_98300EX]

Way late on posting to this, but I just joined.
My FMF Q2 came with the following recomendation, should be a good starting point.
128 or 130 main jet, stock pilot jet and needle setting. open the air box lid / snorkel.
Like you were saying the stock 118 turned my pipe every color you can think of, on a 25 degree day. The color change was almost immediate. I just picked up the 128 main jet and it goes in before the weekend. I will post the result.

[bwamos]

Is he runnign lid or no lid?

you sure it's not an X-4? Think X-4 is the smallest you can get for the 300ex/250x.

Either way, reccomended jetting for a Sparks x-4 w/ k&n and not airbox lid or a vented lid would be a 132-135 main jet. If you are running a closed airbox, you'd be runngin around a 128 main jet

Needle will probably need to be moved up 1 notch. (clip down) and the pilot if it backfires on decel may need to be bumped to a 40 or 42.