It has been a while since I had posted here, but I am having trouble with my 2006 KLX 250 with muzzy exhaust, air box lid off (and lost), smog stuff gone, vent drilled. The bike is ridden 0-8000’ elevation mostly 1000’ - 6000’. Cold weather the bike works fine, but any thing 50 degrees plus the bike pops like no tomorrow. This intensifies with elevation. I think I have a 128 or 125 main jet stock pilot the needle was set per the jet kit instructions and I remember drilling a hole larger per the instructions. It has been years since I had tinkered with the jetting so I don’t remember everything to the tee. The bike worked fine at all temps and elevations for 6 months after I had originally done this. For the last couple years the popping and loss of power has been getting worse. Does this sound like a jetting problem? What settings are people using for 1000’ to 6000’ elevation? Any direction I can get would be greatly appreciated.

 

I sounds like a potential jetting issue but that doesn't explain the drop off in performance. If the jetting was that far out, it would have been so from day 1.

Air filter clean? Sorry to state the obvious.
Maybe some dirt or build up in the carb?
I would give everything a good clean and adjust and then see where it leads from there.

 

Could be an air leak in the exhaust. Check the flange on the header to see if it's tight then where the header meets up with the can. How many turns out on your fuel screw? If that's all good then you probably need a bigger pilot jet.

 

The popping is definately a lean condition.Something has occurred to lean the bike out just a little bit more to cause the popping. Most guys seam to be running a 132 main jet after exhaust mods. Try a jet size a little richer. Old dryed up fuel coating the main jet could even cause that slight difference.Lift the needle a couple thou even. Anyway, the popping is definately a lean condition bud. Good luck and keep us posted.

 

At what rpm range is it popping? That will help determine which circuit in the carb is in use.

If it runs better in cold weather and at lower elevations, it sounds like it's running RICH.

Another possibility, check intake valve clearances. They may have closed up.

Let us know what you find.

Ride on
Brewster

 

I believe I did the standard 2.5 turns out on my fuel screw. I had tried larger main jet and a larger pilot about a year ago and it made it much worse. I had never checked the valves, the bike has about 5500 miles on it and I should probably do that. This is my loaner bike and I never ride it or ride behind it so I'm not sure what rpm range it pops the most. From what I can tell it seems pretty constant at all rpms. There is a bit of carbon build up in the exhaust so I am thinking its running rich. I'll check the exhaust system, clean the carb and check the valves. Thanks for the help. I'll keep you all posted on the progress.