Im wanting to put a big gun es on my kfx 400, someone told me i dont have to do rejetting but im new to the atv scene so i figured it would be better to ask on here to find out

 

Is that a full exhaust or slip on?Do you plan on altering the airbox to get more air into it or running with the lid off. Running factory or aftermarket air filter. They are already lean from the factory. What’s your altitude?

 

It's a slip on. I live in Tucson Az my altitude is 2520 ft...what do you recommend that i do, everything is stock other then the exhaust

 

You might get a 145 &150 mikuni main jet. I’m running a 155 with airbox lid off and yoshi slip on. Your altitude is why I suggest a little smaller