jetting help?

[DIRTRIDER22]

I just put a hmf slip on exhaust on my stock 2007 400ex, Im wondering what size jet i need to up to? I will be running a k and n or a uni with no lid.

[Young_Gun1]

not right now but i can tell you tomorrow! what is your elavation?

[hornetgod13]

42K Pilot and 158K Main would be a good start. Altitude and riding temperature may require you to go up or down one jet size.

[TRXRacer1]

The 38 pilot is fine if you turn the mix screw out a little, go with a 40 or 42 if you want to leave it alone. I'd also start with a 158 main and do some plug chops to see how you're doing. Probably move the needle up one notch too.