Hi all!
On my KLX250 I have a kdx snorkel, UNI air filterand a two bros. slip-on. I did'nt rejet the bike yet (was just about to do it...) but went riding the bike to see how it would run. I'm not a mechanic but I did'nt notice anything wrong how the engines runs. I tried it in many different situations at different speeds, rpms... Even tried to snap the throttle different ways (0 to 1/2. 1/2 to full...) I'm not talking about the performance of course but how the engine runs. I checked my plug and seems all right (little bit brown...) I think it may run a bit rich but probably not a big problem. Is it worth rejetting? What difference would I see if I do?

Anyones advice would be appreciated!

 

I'm shocked it runs at all... It was lean when it was stock.
By opening the airbox and the exhaust like you have, it's now even leaner.
(more air getting in and out, same amount of fuel).

You shouldn't ride it until you re-jet. You can damage your engine from the heat and fuel starvation.

 

im not surprised it runs.... but it will run better after rejet.

 

I put on the Two Brothers can and fitted an OE #138 main jet and junked the airbox lid. OE #40 pilot too. Fuel screw 1 3/4 turns out for now! ( stock filter).
Night and day performance with all the mods. Runs like a scalded cat above 4K.
Not too bad below. Idles fine too.

 

Youmay not need to re-jet Over the past couple of weeks I have been Reserching the subject and this is what I came up with:
1) the bike is jetted for sea level and people say that it is a little lean. Doing the pipe and airbox would require to rejet
2) the higher you go in altitude the richer you get with the same jetting. eg. Stock jetting at sea level little lean---Stock jetting 2000ft above would be a little to rich

So I talked to both kawi dealerships Both said you can fine tune, but at our elevation there is no need to rejet. One of the mechanics I talked to put on a full muzzy with stock jetting and his bike runs perfect!! I say Do not rejet unless nesisary Put on the pipe, install a new plug Ride for a bit.Check the PlugAnd then rejet if nessisary. Do not just do "WHAT EVERYONE ELSE DOES". These are four strokes and should not be as touchy with the jetting as a two stroke. I finally put the two brothers on and have had no issues yet. (only 100km ago) I am at an elevation of about 2200ft.

Ken

 

I double posting I have a good example westOZKLX put the pipe on (leaned it out) then rejetted much richer. and then to compensate for the richness in the jetting had to lean the bike out again by removing the airbox lid... Makes no sense to me?? Can you understand what I am saying!!! Why not just put the pipe on?? the richer jetting is cancelled out once you lean it out by removing the airbox lid???

Ken

 

Ken I just added a new slipon for my bike and she runs beautifuly(with no rejetting).............Even in the mornings now I dont use the choke as long as I had to with the stock pipe. Also with the stock pipe if I let it sit for a bit after riding.........say 2 hours or so when I came back to start the bike I had to use the choke..........not anymore she starts right up and purr's nicely. I have had the pipe on for a few days now and all I can say is wow totaly different bike. I agree with Ken why try to fix something that isn't broken.
Cheers!

 

I was surprised to see how well it was running after the mods (without having it rejetted). I think I don't need to rejet but just was'nt sure if it was good or not for the engine. I'm satisfied with the performance. With what I can read here, I may not be totally wrong. I'm not sure how above the sea level I am here but will surely find it to compare to you guys. That will give me an idea of how lean or rich it was in stock form.

 

i put the two brothers on about 3 months before i rejetted, i am at sea level. with just the addition of the pipe there was a definite change in horsepower and i wasnt sure i needed to rejet nor did i think anymore power could be gained from it.i was dead wrong, the rejet increased power everywhere and i couldnt believe the difference from stock to just pipe to pipe and rejet.these bikes are starving for gas from the factory, opening it up is something you wont regret. pipe is great but without the rejet you are missing out on a ton of potential, at least thats my 2 cents from sea level. dont be afraid to yank that carb, its not fun but its worth it.

 

Kalaski you are at sea level and you should have to rejet, If you read my post, this bike is jetted for stock bike at sea level a little lean, andif you go up 2000ft there should be no reason to rejet, at most install the kouba air screw and adjust it when needed. as you know elevation changes your fuel air mix---well so does ambient outside temp makes a huge impact on fuel mix. I will try to explain: say you went outside in the morning and it is 5degrees celcius the amount of oxygen/ in a certian volume is much greater than if it was 20degrees celcius. or you could say that you will always run richer in cold weather than in hot using the same jetting, this is the reason for the kouba air screw!!!!

Ken