Big Gun jetting

I recently purchased an 01 XR650R with a Big Gun full system. The previous owner put in a 128 main and 68 pilot, but did not uncork the bike. Both restrictors are still in the airbox along with the stock filter/screen. The stock intake (between carb and motor) is still in place also. This weekend I plan to uncork everything and was wondering what jets I should start with. Would a 175 main and 68 pilot be too lean to use with the Big Gun system? Should I try 178/70? Also, what about using Uni filtered airbox vents?


I am running a White Brothers E-2 slip on exhaust and here is my setup if it is of any help.

I used a Dynojet kit, needle, spring and 165 main jet and installed a 55 Kehien pilot jet. I did not drill the slide as is so often mentioned as a necessity. Then I ground off the air fuel screw tab and bottomed the screw out and then back it off 2 1/4 turns. I then Removed the stock air filter and replaced with a UNI filter, removed the top of the airbox (snorkel), removed the smog equipment and blocked off with an IMS kit.

Runs great! cold starts vastly improved as is cold running overall. Pulls strong and has crisp throttle response.

If you plan on cutting side cover and no back fire screen you should try a 190 main move needle up one position.:applause: I always ran stock pilot but bump it up one size to make it run right.

Thanks for the help, guys!

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