Very Lean issues
 

I have a 2009 KLX250SF. I live at about 350ft ASL. Snorkel off, Big Gun Evo R exhaust slip-on.I have a 17.5 pilot jet, 130 main, and the stock needle jet and jet needle. Jet needle is all the way to clip 5(lowest clip.) Went for a run today it was about 65 degrees and it stalled along the way. Started back up after about 10 minutes. Took off the tank and checked the sparkplug. White/Grey. Couple dark spots that looked like speckles. I checked the rubber boots and they look to be tight. Am I missing something?

The dark spots make me wonder if its too rich? Since it took 10 min before it would start again sounds like it got flooded. Are you running a DJ kit or Keihin Jets? Another area to check is the float level. It may have become bent when re-jetting causing a lean condition.



I would try running a smaller jet and setting the needle to the 3rd down from the top and see if that fixes it. While you have the carb off check the float level. Also replace the plug. If you have the factory tool kit you can change the spark plug w/o removal of the tank. I did it on my lunch break in the parking lot while it was raining a few weeks ago.... :-D

Here is my setup for reference and it runs as smooth as butter!

09 Klx250SF
LeoVince Exhaust
Stock Air Filter
Snorkel INSTALLED

DJ Main Jet DJ120
A/F 2 Turns out
DJ Needle 2nd clip from the top.
DJ Spring

Cheers

J

I forgot to add that the carb isn't a CVK34 anymore, it is a TM-36-68 A/P. The main jet came stock at 130, but the idle would drop very slowly when I gave it throttle and my friend owns some harley's and had a left over 17.5 Mikuni pilot jet that he let me use, it was a 12.5. But from what you told me about the dark spots im going back down to the 12.5 and going from the 5th clip to the 3rd and see what happens. I thought it was lean because when I went for a ride it felt like it was hauling ass. Lifted the front wheel off the ground a from first to second gear. And I'm going to check out that factory kit cause taking off that spark plug is really becoming a chore.... I've also lost like a gallon of gas from constantly unhooking the fuel tank about 20 times.

"it felt like it was hauling ass", if the bike runs like that your close take small swings from here on to get it perfect.

What HE said ^^

And I have a TM36-68. FOR ME the 17.5 is perfect. I had to go to a P6 needle jet because it was too rich just off idle like around 1/8 throttle.

Start with a fresh plug. I would not worry about checking the plug it does not tell much unless you are REALLY rich.

Look here for advice on tuning a carb.

Mikuni American Corporation

If you are too lean, there is another reason. That carb box stock is plenty rich for our bikes.

David

Yeah it was hauling ass until doing about 50 for a mile and the thing just died. hope my timing is still good...

Dave is your bike still a 250cc?

And what's the difference between p6 and p8 and so on? That's the jet needle.

What about the needle jet? For a stock 250cc do I need a different one?

Wow when I thought everything was going a little better, around a mile out my bike studdered again and stalled. This time it started up immediately, I hit the throttle just a touch and it died. Started right back up, I touched the throttle a hair and again - dead. Maybe this p-6 thing is really all I need. Ordering it RIGHT now.

You are describing a starving for fuel situation. No matter what jet you use the bike should not stall going down the road. Plugged filter?

"Hit the throttle just a touch and it died" No fuel in the carb.... Starving from supply not jet issues.





P6 is supposed to be a leaner NEEDLE JET. P8 left black soot on the back of my bike and fuel mileage was in the fortys.

With the p6 the bike has crisper throttle and gets around 60 mpg.

David

I already ordered the part so oh well - want to get a 351 kit sometime next season so might work for me then so I'll hold on to it. But now I'm REALLY confused.

Now my concern.

So I may be starving it. But with the 17.5 and 130 jets shouldn't that be plenty of fuel?

I also tried playing with my A/F screw. Tried everything from 1 1/2 turns to 3 1/2 turns. I felt very nice around 2 turns. Kept it there. So there should be some deliverance there.

Looked in my exhaust after hearing about your soot. Yes I do have a lot of black in my exhaust header. One thing i noticed that freaked me out were these little almost silver looking shaving. When i touched one it completely disintegrated. Don't know what that's all about.

Spark plug color I checked is still a gray with speckles of dark brown. Thinking about making a movie on my phone and putting it on youtube. I feel like I'm missing some important information that you need, that only could be shown.

Have you checked the float level?

Here is a good guide for checking it.

Factory Pro Float Height Tuning

As for the special tool a simple dial or digital caliper will do the trick. (I got a pretty sweet one for $20 at harbor freight)