KLX250s exhaust and jetting
 

I have a 2009 klx250s and just put an hmf pipe on it. Do i need to re-jet the carb or not. if so, any recommendations on how to do it.

How does it run? If the flow through the pipe is nearly the same as stock (which I doubt) then you should be pretty close as is. However, if you are moving more air, then I suspect you'll be running a tad lean until you bump up a few sizes in the jetting department. Make your "observation" runs when bike is warm, and be aware of revs from "hands off" idle through high rpms. Check your spark plug color and see what this tells you, as well. Darker is richer; lighter is leaner. You want a nice light tan to brown color. If the KLX is a 2 stroke (hey, I ride an old Husky; I don't keep up with the new stuff) and you see oil residue on your plug, you're running rich OR using too much oil in the pre-mix. Make notes of anything else which has been changed, as well as outside temperature and humidity. Jetting is affected by temp, humidity, elevation, etc.
Let us know what you find.
Hope this helps. Welcome to KF!! Gear up; stay safe.

I will bet my bike that that plug is white unless someone has put a jet kit in that carb. Do yourself and your bike a favor, get the Dynojet kit and go with the stage 2 settings. The bike is lean in its stock form and needs more fuel as it sits! The jet kit is one of the best and most bang for your buck upgrade for our bikes.

I agree. lean from the get go. Bump up the jets a couple sizes and then do your plug chop. Needle tapers, spring tension and any other fine tuning can be done later.

Thanks for all the help. Decided to go with the dyno jet. Installing it was a little over my head(its a new bike so i wanted it done right) so i just dropped it off at the shop and should have it done by monday.

Nah ya could have done it. There is a step by step or close to it on here somewhere. Remember as soon as you add something else to the bike (head pipe, better flowing air filter, etc.) you will more than likely have to do some more jetting fine tuning of air screw adjustment. At least you would already know how to do it.

Glad to hear you're getting a fix. However, I agree with slippery; don't let the psychological threat of "now what??" get in the way of doing mods yourself. Sometimes that's exactly why the new found skill sticks in your brain cells. We're here to offer advice and help. Let us know how she runs when you get it back!!

Well i really wanted to do it myself and now i wish i had. The only reason i didnt was because i didnt want to mess up something and end up paying even more to have my screw-up fixed. Now I really wish i had just jumped in and done it myself. In the future i plan on doing all the mods myself. And when i do, i'll probably spend a lot of time on this site.

Thats the attitude! Do a search if nothing, ask the question...Were here to help!

New Two Bro.'s slip on - bike stalling
 

I just put a Two Bro slip on exhaust on my KLX250SF. I really like the sound of it and it runs great UNTIL I get about 5 miles in on a steady 55 mph ride and it stalls like it is out of gas. I did not rejet and I assume the new pipe with the increase flow through is really throwing off my fuel mixture and when it gets good and hot it chokes out the carb?