Rejetting needed for a cam?

[ZSK]

I was wondering if I needed to rejet for an aftermarket cam? I picked up a hotcam stage II and a buddy told me to go up 4 sizes on the main and one notch on the needle for the cam break in and then go from there. Any truth to that?

[cals400ex]

with my cam and piston installed, i had to go up 1 size on the mainjet from where i was at before the install. i don't think you need to go up any near 4 sizes, but you can try it if you want. it will probably run fine with the jet you have in or 4 sizes larger. for the bike to not run good at full throttle, you need to be off quite a bit.

[mikeminyard]

I didn't have to touch my jetting with just the cam.

[Colby@C&DRacing]

If your jetting is right now you will not have to change it with just a cam:)

[04-KFX400]

The fuel/air is mixed (in the carb) before it gets to the valves so, if the mixture was correct before the new cams, the new cams would only allow more of the correct mixture to enter the cylinder.

Re-jetting would not be required.