Stumble between idle and mid throttle
 

2007 KLX250S (std bore)
4700 miles on odometer (bike's condition reflects the mileage)
~4000 ft above sea level
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KDX200 snorkel
K&N air filter
Dynojet 2152 kit with 128 main
All smog crap removed and capped
OEM header
FMF Q4 slip on with 1 1/8" quiet core


Bike idles smoothly and once hard on the gas it pulls as well as can be expected from a 250cc bike. Somewhere between open and idle is a catch.. the bike stumbles a bit almost like a two stroke.

Note that if I accellerate from idle to full throttle, the bike pulls clean. The stumble/catch happens when the throttle is chopped and I reapply throttle. On the ride home yesterday, the stumble after chopping throttle caused the bike to die. It started back up with little fuss.

What could be happening?

Oh no.. Not again.. I certainly hope you don't have the disease PWJM and Snowdrifter had..


I worked with PWJM for over a month trying to cure his stumble problem. We ran outta ideas and posted his plight for forum help - https://www.kawasakiforums.com/forum...welcome-43229/

Snowdrifter also had the same problem. No solution was ever found. They both replaced the CVK with TM36's.

Snowdrifter sent me his CVK - I took it outta da box, put it on my bike, and it ran perfectly fine. So, I'll send this link to ya as well - https://www.kawasakiforums.com/forum...s-fixes-43146/

I've added a few more details to the top post.

Did the DJ kit include a larger pilot jet? My bike had the problem of cutting/strong hesitation when blipping or even rolling throttle aggressively from idles/lows. Like it almost wanted to die then a strong surge after.

Going to a #40 pilot and fuel screw about 2 turns out completely eliminated the problem. Thats at 35' above sea level though.

the DJ 2152 does not include a pilot. Still stock 35 there. It looks like the 35 is what most people end up using even after experimenting with a 38 or 40.

Depends on your altitude. 40 definitely made my bike both easier to start and completely eliminated the off-idle hesitation.

What is your elevation?

BTW-- I have also experienced the "single spark cutout" under hard accelleration at around 7K rpm or so that others have talked about. Only happens about 10% or less of the time, but seems to happen about the same time in the rpm range everytime it does happen.

Very odd thing is that my previous CRF 150F dirt bike had the very same cutout doing the very same thing at about the same % of the time. :confused:

You may be rich on the main while running the lid and kdx snorkle. Pull the snorkle then the lid and see if that improves things. What needle clip position are you running?

"What could be happening?"

You are running the DJ kit as per instructions for stage 2 I believe - this is a known working setup for the CVK.

It wasn't happening before you took the carb apart. The setup parameters (Stage 2) are not to blame. Seems something "went wrong" between the moment you started taking it apart and the moment you finished putting it back together.

Sticking slide? Perhaps due to incorrect slide spring indexing on the cap?
https://www.kawasakiforums.com/forum...s-fixes-43146/

40 pilot here too, 2.5 turns out on the idle mix screw. 900-1000 ft elevation but been higher.

KLXter is the go-to for the Dyno-Jet stuff. He does go without the air box lid which is fine for road and those who don't have any concern with water splashed over the top of the air box.

I'm also running #40 pilot but It's certainly not needed unless decel pops can't be cured without it. It does give one the ability to fully control the AFR of pilot circuit operations/running. Only other interesting function of the pilot system is its' "transition" ports. Those ports simulate an accelerator pump function - providing a little "shot" of AF every time a closed throttle(butterfly) snaps open - in the microseconds it takes for the slide to react, high vacuum draws this little "shot" from these ports. So you get a bog-free rev-up..