Hey Guys!
So I just picked up a 2007 KLX250. When I got the bike the guy said it ran well in first second and third gear but 4th and 5th were bogging. I took apart the carb, looked through it, and cleaned out all the jets, ports, checked the diaphragm was working, made sure I had no vacuum leaks, new spark plug, and clean air filter. Now he's the problem I'm running into. When I threw the carb back in it started amazing but when I rode it, it liked to bog in first and second but when I got higher rpm and higher gear, it cleared out. So I decided todo what most people would do is mess around with the air/fuel mixture screw. Managed to get a small flat head bit in there and enriched the mixture. Now it ended up getting worse so I leaned it out, also made it worse. Now after trying to get it right I somehow got to the point where I try to take off on the bike and the second the clutch reaches the grab point, the bike bogs and dies. The thing is I can rev the bike perfectly at idle and it wont die and it sounds healthy. So now I'm super confused, is it the clutch? is it the carb? Im totally lost and I would appreciate some advice.
Thank you!

 

I only know a little about carbs, but here's a few things to look for...

How high is the level of fuel in the carb bowl? Is the float adjusted to the proper height? Is the float valve sticking in the closed position? Does the needle rise along with the slide when you twist the throttle? Was the diaphram and spring properly assembled, and did the diaphram completely seal on assembly? Were there any tiny ball bearings positioned in the carb when you disassembled it? Also did you blow out all of the passages in the carb with compressed air?

I'm sure others who know more will have other things to check.

Let me know what you find.

 

it sounds like the idle circuit may be partially plugged. I've seen a whole lot of bikes of all sorts that had problems like that after sitting for long periods of time when I worked at a bike dealership. The fuel in float bowls dries out leaving a residue that turns to gum when gas gets to it or flakes off getting into the idle circuit and starter circuit, clogging the small passages. The best thing to do is what was done there. Tear down the carburetor and have the body cleaned with a carb washing machine or an ultrasonic cleaner to work the solvent into the passages. That may require taking the body to a car or bike shop that has the cleaner machine. There were times it would take recleaning. Running wires into the passages can damage the surface causing worse flow if you're not careful trying to clean them on your own.

If you do decide to try deeper cleaning yourself again I have done so with a gallon can of cleaner. I used Berryman cleaner, has a basket to drop the parts down into the can. Protective latex gloves are needed, the stuff is pretty strong. The carb body can be put in the basket, the lid put on securely, and the can shaken to get the cleaner through out the carb. If you use the cleaner read the directions, there may be instruction about how long to have parts in the solution. It did the job cleaning the stuff up on an XT225 carburetor that had been sitting with the gas in it for several years. The stuff in the float bowl had dried out leaving an almost brass shiny layer of residue on the surface.

To make sure your carb is set up well, with correct jetting, there are two sources for carb jetting. One is finding a couple of the threads in this forum for the Dyno Jet stuff. The other is to look at the web site of D. Pippin at his KLX250 Information page and it is specifically on the 2007. His section on the carburetor has the section on jetting modifications. My brother (2006 KLX) and I (2009 KLX) found his recommendations to be pretty much plug and play, including the idle mix screw setting. Click here to get to his site.

 

Did you remove the pilot jet, run a wire brush bristle thru all its" tiny holes, and visually verify that it is clean and completely clear of obstructions ?

If not, then do so now.

Also, check the transition ports for obstructions - these ports create fueling as the throttle is opened slightly off idle.

Also, probly outta read my link below on CVK problems..