Road my 2007 KLX around our alpine loop, a pretty rough 4wd road over a couple of high altitude mountain passes in SW Colorado. About 57 miles total. At the top of one of the passes near 13000 ft, I let the bike idle while leaned over on its stand, for about 10 minutes. After a short distance more riding I smelled fuel, and saw fuel dripping from under the engine. As it was downhill and on the way home, I kept riding. The smell and leak went away. My buddy thought that it might have been because of the idle-ing, or the step ascents we had just done. When I topped off the tank, the fuel use was 1.3 gallons over the 57 miles, or about 43mpg. A subsequent set of rides over 50 miles, (flatter, no super steep terrain) saw no more leaks, and burned .9 gal over 54 miles for about 60 mpg - about normal. So the .3 gallons lost on the trail is significant and worrisome. Especially given the NO gas stations or help in our backcountry. Any ideas of what to look for or why/what happened here?

 

I know my KDX220 will keep filling the float bowl and drain when the bike is parked with a more than usual lean. My KLX has a good lean when parked, but because of the gear I carry when out exploring I watch where and how it's parked. Main reason is because I mount the bike like a horse due to the tail bag.

 

The fuel level on your carb is set too high. When the bike is leaned over, the float thinks the bowl is draining and tries to fill it, but it is overflowing out the overflow.
Easy fix: When on side stand for more than 1 min, shut it off and turn the fuel off.
Otherwise: Remove the carb bowl and adjust the float level. You'll probably have to take the carb off to do it right.

 

When my 2009 SF has the dirt wheels on it with the SF kickstand, I use a wooden block when I park it.