Seems pretty straight forward, no? Follow the directions in the kit and go. But nope, something isn't right since I put the 300cc kit on. I have a jet kit for a KLX300 and a Big Gun pipe (full system). Recently the bike has been running sort of crappy, lots of stalling after decelerating and a hanging idle. After a bunch of adjustments I added a larger pilot (#40), helped some, but not enough and I noticed the tail fender was black.

I just went out for a 30 mile road ride, some highway, local roads and dirt roads. I get home and the tail is now melting! WTF? Pull the plug, looks lean, not really lean, but lean and the bike stalled at more than one stop sign, the idle would drop to about 2k and then settle after a few seconds.

I tried putting the airbox lid on, worse, I also noticed with or without the lid on, giving the bike a short throttle crack would cause it to hesitate a little and then rev fine, sort of like a pause, which maybe is just a CV carb being a CV carb. So I tried pulling the DB killer out of the exhaust and went for a ride. Much better, no stalling and the exhaust/fender is not hot, but a fair amount of pop on decel. There is still a slight pause when I give it a slight throttle whack off idle, but it is not hanging anymore. I also noticed if I whack it WOT out of gear it will break up a little around 6-7k and then hit the red line, if I do this while riding, it is fine.

Something just isn't right. I checked for air leaks and cannot see any. I have the main jet and needle set per DJ's instructions for an after market exhaust with the lid removed, so I am thinking my problem is mainly with the pilot, but which way, lean or rich?

Here are my settings, I am at sea level:

300 cc kit
Stock air filter
Airbox lid off
Crank breather and other emmission mods done
DJ 132 main
#40 Pilot
2 Turns out of the mixture screw
DJ needle on the 3rd clip

Any advice would be really appreciated.

 

swap out the 132 to the 128 per the instructions. also, put the 35 pilot back in and make sure the needle is fully down in the slide. there are notches that the needle holder falls into at the bottom of the slide. make sure the needle holder issitting in the notches.
I was having problems with my bike too similar to yours except that mine would bog at mid throttle. I had the 132 in and notch on 4th. I swapped to the 128 and lowered it to the 3rd notch and turned the a/f screw 21/4 turns out. It's absolutely flawless now. I have a kouba on the way but honestly I don't think I need it now. I'll use it to fine tune the a/f mixture but I seriously wouldn't want to mess with it now. also, make sure your clamps around both seals at each end of the carb are tight and are as far on the carb as possible. a new spark plug woudn't hurt now either.

 

But you have a 250 not a 300 right? I ran the 128 and needle on the 3rd clip as DJ said and it was worse. The 132 on the 4th seems to run better. My problems seem to be mostly on the pilot. Checked the boots and vac nipple, they are secure.

 

It sounds like you might have a diaphram problem. Even a small pin hole with mess it up. That, or it's not seated all the way in the grove.

 

Recently i was *Trying* to fine tune my jetting.... i got called away for something, and did not put my diaphram in water..... it expanded a bit not much , if it does not line back up in teh grooves you will get a vacuum leak or whatever you call it... so i'm probaly gonna have to order a new slide... go me , i'm excited , cant you see.... I tried to put it back in , i thought i had it , but i didnt it ran like crap because it wasnt lined up with the grooves...

 

I am going to check the white needle cage and diaphram. I am pretty sure you can put the diaphram in the freezer or cold water and it will shrink so long as it isn't ripped.

 

You can put them in freeezer? I thought about it , but wasnt sure if it would damage it.

 

I have your same setup. Run the 132 on the 4th groove. As Tremor said--hanging idle = diaphram problem.

 

More and more that is making sense. Good thing you can pull the cap off the carb with it still in the bike!

 

just for reference I was running at 300cc with oem jets as follows
138 main
Needle 4th
37.5 pilot
2.5 turns out
Weather was a little on the cooler side but the bike ran strong.