I am putting on a billit exhaust end cap. It has a 3 times larger opening than stock. Everything else it stock, but I may be putting on a K&N filter. Will I HAVE to re-jet?

 

the end cap wont really make any difference, but the K&N will cause you to have to rejet

 

I agree the end cap wont make much difference. Since they come a little on the rich side from the factory you may not have to rejett with the K&N either.

 

I thought they were LEAN from the factory to meet emissions.
Thanks for the input. I'll try and run it and check how the plug looks after a ride..

 

Please let me throw my 2 cents in here: I highly recommend a rejet regardless of what you do to your machine. My BF started running bad like it had trash in the carbs, I went ahead and ordered a DynoJet ket and figured while I had the carbs off I would rejet. I have stock air filter and stock exhaust, just from the jet kit the difference is awesome! No more burning the left leg either! Then last week I added the VDI module, from a 10-15 mph punch the bike will stand the front end and walk a wheelie, the power and response is unreal. It's like a totally different bike.

Mike

 

Altitude plays a big part on how the quad runs with stock jetting so what might be good for me may not be the best for you. As a general rule they run them a tad rich from the factory because its safer on the engine to run rich. They know about the worst damage a rich mixture will do is foul the plugs and loose performance.

What quad are we talking about anyway??

 

Sorry for not listing it. I have a 03 KFX-400.


I live at 500 feet, but do most my riding around 3000-5500 feet. It runs real good with the stock setup, but I am wanting to try and get everything I can out of the stock machine..

 

To get the most out of it at 3000-5000' you should be running pretty lean at home. As you go higher the mixture will richen do to less air at higher altitude. So in that case I would not rejet with the K&N. It will not lean it enough to hurt anything and will run better at higher altitude than stock.