I bought a 2007 KLX250, the previous owner had swapped out the stock exhaust with a FMF Q4, and removed the airbox top. Everything else is stock. It seems to run well, no problems starting etc. Im in Arizona at 2100ft altitude.

I was wondering if rejetting with a dynojet kit or similar would be worth the trouble. I'm not really sure what size jet would be best for my situation.

Also, I saw that a lot of people run a new line from the crankcase to the airbox and add a bolt-on filter. Does this really make a difference? Seems like it just moves the intake from one filter to another.

Any insight would be appreciated.

 

Based on your mods I would think the previous owner already had to rejet the carb. Are you experiencing any performance problems, which is why you want to rejet?

 

For sure. If it's running good with a Q4 and no airbox lid - it must have already been rejetted. Easy enough to check - pull the carb and check the MJ and needle. Pilot should have remained a 35 anyway.

 

I personally didn't touch my crankcase vent line nor will I... for what that's worth.

 

I'd be surprised if it wasn't already rejetted by the PO, but yes, it is almost essential with an aftermarket pipe.

 

Im having no problems, I had just heard it could add a little pep. I'll take a look and see if I can figure out it it's already been done. Is their an easier way to tell than to remove the carb? I hear thats a pain with this bike.

 

Can you get in touch with the previous owner?

 

No, you'll have to pull it out and look at the main jet size. At that point you'd might as well have a Dynojet on-hand in case you need to change anything. If the bike is running good throughout the full throttle range your fine.

 

This is what happens when people don't use the stickers included with their mods...

 

Well, you could just pull the top cover off the carb while still installed and check the needle to see if it's a standard KLX needle or if it's a dynojet needle. I'm sure if you have a DJ needle you also have the DJ main jet as well.

IIRC you need to remove the seat and tank to get to the top of the carb. Way easier than removing the carb itself.