2007 KLX250S Hard Cold & Hot Start
 

Not sure why it is so difficult to start my bike. I have completely cleaned out the carb, the fuel tank, replaced the fuel filters, replaced the spark plug, and replaced the battery. Sometimes it starts on a cold start, and when it is running I can ride it around and the bike sounds and operates phenomenal, there's no problems there. This bike only had 105 miles on it when I purchased it off a gentleman who has had it stored for a while (the fool left the tank and carb full of nasty fuel - so I picked it up for $750). I did notice that the carb's fuel mixture screw has never been popped/tapped off, so maybe the fuel mixture screw was set too lean right from the factory? I can adjust the throttle down to about 2200 RPM and it slowly drops down to about 1300 RPM and dies, which then I can not get it to restart. I am afraid to pull the cap off for the fuel mixture screw and cause potentially worse problems for myself. Any ideas on what I should do?

Carb still has gunk in it. Some little orifice in the pilot circuit I'd say.

I just can't see this being it. I was pretty thorough on cleaning it, I even ran wire through all of the orifices and jets to make sure they were clear...

Tight valves?

I've heard that a clogged pilot jet can be a bugger to clean completely, and to just buy a new one and be done with it.

If the carb was that bad, maybe it needs a good overnight soak. Read before of soaking in pinesol and also boiling it in water. Agree that it still sounds like a carb thing.

Check all the vent lines, make sure nothing is plugged or pinched.

Does it make any difference if you open the fuel tank lid (not venting properly)?

I'd pop off that fuel mix cap also. Just follow directions and be careful.

I am about positive the carb is clean, I used carb cleaner, soaked it, and blew it out with my air compressor until all of the opening and jets were free for me to run wire through them. I saw where some people were boring out their enrichment jet with a 0.018 drill bit -- would this be the advisable thing to do?

Enlarging the enrichment jet (refered to as the "choke") will help starting but not the problem you're describing.

Right, I was just thinking about that, the bike tries to start just the same choke or non-choke, so it's got to be the fuel screw? Also, when installing the main jet and starter jet, is there a certain tightness that they should be at?, because I just stopped when they both bottomed out. My only thought now is that it is a factory f-up, and to pop the cap off the fuel mixture screw and mark where it is at and adjust accordingly.

Could it also be possible there's some blockage at the fuel screw that didn't get cleaned out?

I was thinking the same thing. There are some small passages in that circuit.