After going 128 main jet, fuel screw 2 1/2 turns out, airbox lid off, TwinAir filter, and full 09 muzzy, the bike feels like a 50cc scooter. If I roll on the throttle, not much happens. I'll slowly get up to speed, and max speed is about 55mph. Struggling to get up hills. Stop and go is fine, but overall the bike is smooth, but very slow. Again, I struggle to get to 55 mph max speed. With wind probably 50mph. A hill I'll drop to 45 mph max speed. I'll roll the throttle all the way and there is no change. The bike was running fine before this as stock. I would get some slight stutter at highway speed but I think that just it's lean nature. Not sure though. I also pulled a main jet out that said "K118" on it. Is that the stock normal jet? Also, the fuel screw was not covered. It was already accessible. I got my bike used at 1000 miles.

However, twice, I was steady on the throttle at about 55mph, when all of a sudden it made good power and I shot to 65mph. It was for only a second or two. It did it again a few seconds later. After that, same old scooter feel.

Someone mentioned that perhaps the floats were not moving freely. Someone also mentioned to check the vacuum line. Where is that?

My elevation is about 600 ASL. I don't believe I have any air leaks and to me I think I am running very rich. No obvious popping but I thought I had maybe heard some on deceleration. It's my first bike and first major mod so I may have just been hearing normal deceleration noise.

After taking the airbox lid completely off and turning the fuel screw in a little to 2 turns out it helped the situation very slightly. I replaced the stock screw with a Kouba. The Dynojet kit came with their own but I didn't use it. The new Dynojet kit for the KLX does not involve drilling out the slide. They simply provide a new spring for that.

It started right up and idles perfectly. I really like the sound of it. If I could only go fast!

Any suggestions to try before pulling and opening the carb again?
What's a good way to test for air leaks?

 

Something definitely not right. I'm not sure I completely understand the sequence of events - did the bike do this when you bought it? Or only after installing the dynojet kit? If the latter, it sounds like something may be amiss with the diaphragm. They are tricky to get reinstalled correctly, perhaps a small tear in it or something is the culprit. It sound like it cannot move freely enough in order to rise under engine vacuum. A small tear might make it act that way. That is where I would look first.

 

Editing my post.

Put your airbox lid back on, remove the snorkel, and turn your screw to a full three turns and see if thats better, then try 1 1/2 (see below why).

You should get a aftermarket air filter and your gonna most likely need a larger main jet almost for sure in there. Along with a bigger pilot. UNLESS yours is like mine and you already have a 38 pilot in it. I'm seeing a pattern here with some KLX's like this. But with all that your going to almost definitely need to have a 40 pilot in it. Where is your needle set? Is it in the 3rd clip? Your gonna need to put it on the 4th clip most likely.

 

The bike was normal as stock. Except for slight highway stutter occasionally. Say I figure out the problem here, will I have to rejet if I remove the smog system. I forget if there's really any performance gains from removing that...maybe I'm thinking of the crank-case breather mod.

 

the smog removal and crank mod seemed to me that it helped it rev harder and higher. More vibration as well.

 

+1 on what Nobrakes was saying about the diapram. I'ts worth the time to pull it back out, check for any pin holes, then carefully re-install it making sure the lip is fully engadged in the grove when you put the cap back on.

While you have it carb open, double check that the the dynojet needled fully settles into the slide and seats into the needle jet at the bottom of the carb bore. Sometimes the dynojet needles need some emery cloth taken to them before they will fully insert into the slide.

If the bike starts easily and idles well, the pilot jet shouldn't be much of a worry .

Good luck!

 

my bike has a 128 main jet, stock pilot, airbox lid without the snorkel, needle on the second clip, and a/f screw 2.5 turns out....

Everyone elses jetting is a starting place, thats where "you" have to take over and see how it runs then adjust it from there... i think everyones messed with thiers a bunch of times... what you have is a starting point and now u have to fine tune it, but somethings not right, like already stated, id check the needle and diaphram

 

I just thought of something. There was no cover to the fuel screw. Unless the factory doesn't cover that up anymore the previous owner drilled it and messed with the screw.

Is it possible that he drilled the slide hole too a la KLX 300 dynojet kit? It definitely looked like the stock needle in there, but I did not verify the size of the hole.

What is the size of that hole in stock form?

Suppose the guy had drilled the hole like the KLX300 kit calls for, but ran a stock needle? Suppose I put the 09 Dynojet needle in there?

Would that just be too open and a vacuum that is too weak to raise the needle?

I will be very mad if the dealer sold me a bike with a screwed up mod.

 

I really really don't think at this point you can go saying you got holes in your diaphram. I mean, it may be...but I seriously doubt it.

You got the lid off and a full exhaust and your running a stock needle, stock pilot and only a 128 at 600 ft in November temperatures. I think your running lean. Plus, you said before it was running fine before except at highway speeds at which it would stutter like alot of others do because of the small main jet.

My moneys on you runnin' lean bud.

 

I'm running the dynojet needle not stock. Temps vary a lot here in Texas in November. 50F nights, 80F day.