I have an 06 400ex and i was wondering if i bought a stage 1 hotcam, would i have to buy a big bore kit or would i have to just rejet it? I plan on buying a 426, but for now i want a hotcam. is this a problem?

 

The cam will help some without anything else. You don't "need" a bigger bore, but more compression to help the cam is always better. 400ex is like 8.5-9.0 to 1? 10.5-11.0 to 1 will wake it up with a stock bore.

 

i had the stage 1 cam in my ex, and the only way to achieve a good gain from this cam is to put a full pipe, and open up the airbox. for that you will need to rejet. a cam swap is un necessary to rejet if thats all you are doing. also if a 426 is in the worksa stage 2 would be the ideal setup for it. also keep in mind that a 426 is the last bore you can go before resleeving the cylinder. i would look into a 416 first with a stage 2 and open air box, with good filter and full pipe. if i didnt get rid of my EX that would be my ideal set up.