300ex jetting

[Pvt. Maggot]

i'm rebuilding my 300ex i have a 20 over high compression piston..stock header with a t-4 shorty slipon and i'm gonna run without the airbox lid...what jetting should i run? i'm stock right now..i'm in PA if that helps any..thanks

[ZSK]

Try a 140 MJ and a 2 notches above stock on the needle should be close probably too rich though, I've got FMF full system, no lid, K&N. I have a 132 and that's perfect.

[cals400ex]

i would think that would be too much. when i added a high compression piston and cam in my 400ex, the jetting didn't change much. removing the airbox lid changes it just as much as the cam and piston did. i would try around a 132 or 135 at most for starters. jetting is trial and error. for the needle i would lower the clip to the 4th position and see how that works.

[ZSK]

I didn't know how much the piston would add. I posted what I've done try a little more than that.

[MichaelS693]

128-132