I have 2013 KLX 250 just got a fmf powercore4 slip on and want to Jett it to next size up.. What is the factory jet size now? Thanks

 

Best to go to the FMF website or call them to see what they recommend. It will almost surely be more than one size up.

 

Your idea of going one size up on main jet is on the right track but no where close to what is needed once you ditch the stock slipon for a PC4. Are you going to modify the induction system, e.g. snorkel in or out? Lid on or off?

 

the stock jet size has numbers "118" on the jet.

buy a dynojet kit and have it installed you wont be disappointed.

it cost me $168 to have one installed , and have the carb cleaned.

no more cherry red exhaust.

I still have to put the choke on to start the motor, after the motor starts I can rev the throttle a couple times and push the choke in, and the motor idles always.

dynojet has the instructions on there website, for sure worth the money and makes the bike more enjoyable to drive.

but also remember the dynojet kit changes everything so I wouldn't reference the numbers from dynojet if everything else is stock in your carb.

the dynojet kit replaces the needle, spring slide, clip, and main jet.