I posted a thread last week where my new to me 2003 was running badly WOT at 10,500 feet. http://www.klrforum.com/showthread.php?t=23570

Got lots of useful ideas (thanks!). I recleaned the air filter and oiled a bit less with Motul & cleaned out the passages in the fuel cap. More parts in there than a Swiss watch. It wasn't plugged, but was varnished up enough that I'm glad I cleaned it.

Fortunately now it's running badly at 5000 feet which is easier for me to work on.

Blasting along I-70 at 75 mph WOT slowed down to 65 when I went up a slight grade, (90F / 500ft). I got the surge and stumble and overheating. Did some research on the surge and stumble & it seems to be vapor lock where the gas boils in the tank & probably the carb bowl. Opened the tank (no hissing) and sure enough it was boiling away. Glad I wasn't smoking at the time.

Fan works fine. Will do a coolant flush just to be sure....

Other thought is that the main jet has crud in it and it runs lean at WOT. I'll pull it out and clean it & check the size.

Anything else I should do this week?

Thanks, Wray

Traced though the air/fuel/exhaust/ignition systems--everything looked OK except for some black particles in the carb bowl. Figured it was either the 10 yr old fuel line or the petc0ck rubber bits. Replace the fuel line.

Used the mighty-vac to pull a vacuum on the petc0ck and it wouldn't hold vacuum. Seems like it ought to or I'd have unmetered air going in to the carb after the venturi. Also a leak at low vacuum (WOT) would cause it to not open up all the way.

Replaced it with a manual one from Eagle Mike & it ran great.

In the one step forward/two steps back department, when I got off I-70, the bike quit--the float had stuck open and was dumping about 1 gpm of gas through the carb vent tube.

Did a PITA roadside carb bowl removal and wiggled the float & it ran fine to home. Best guess--prolly got some dirt in the carb bowl from the new fuel line or petc0cok or the on-bike disassembly of the carb to check it for cleanliness.

Thought I'd pass the vacuum petc0ck findings on--I've replaced a bunch of them for fuel leaks, never for a vacuum leak.

If I'm missing something on the "not holding vacuum" bit, please let me know so I can further my KLR education!

Thanks, Wray

Good call on the petcock. Not holding vac means diaphragm is leaking.
Regards....justjeff

Thanks! Always helps to confirm suspicions.