torque loss, and engine shut down
 

While driving home from work yesterday, I felt a loss of torque. Looked down saw RPMs dropping and pulled over on the side of the highway. My engine died and I was unable to crank for about 5-10 minutes. eventually I had to swap over to the reserve to get home. Could anyone please tell me what might be wrong, and if I can leave the bike on reserve selection and use the full tank until I get the problem fixed? Any help would be great.

Unable to crank as in the motor wouldn't turn over? How's the oil level?

Some petcocks are vacuum operated and if that part of the petcock fails, it may not flow adequate fuel in the normal on position, but may flow in the reserve position (my KLR has this type of petcock as stock).

would not crank...pressed the ignition, turned over but would not start. after a few attempts, and letting it sit for a bit, it would start.

i just returned from the motorcycle shop, talked to someone in service center. he is pretty sure my fuel level was in between the normal tank feed and reserve feed; i guess there s a dead space that i happen to get stuck in. i have been driving around all day with the tank in reserve selection and have had no issues. he also said, if i was experiencing the same issues while in reserve selection, then it would be possible that the fuel filter or pump could be going bad. both feed lines run through the filter and pump. i was only experiencing in normal selection.

my ex 500 will do this in hot weather as well this last yr. on start up. Place the petcock to res, crank the engine over a few times, it will finally fire up. ( I believe the tank gasket is bad which causes a pressurization issue to the vacuum operated petcock) So, I would replace the tank cap gasket, double check your hoses for any kinks, and rebuild the petcock. Cheap repairs to try.

There might also be a split in the filter screen on the fuel pick-up. Normally the screen prevents air from getting sucked into the fuel lines so long as the screen is at least partially covered with fuel, but if there's a split/hole in it then it will suck air instead and can allow vapor locks to happen at much lower temperatures. Clean and check the petcock/fuel pickup to find or exclude the problem.

Thanks for all the information and ideas. I will start running the gauntlet this weekend. I did ride it to work again today with no issues. I really hate not knowing what caused the problem yesterday. If I find anything, I'll post. Thanks again for all the help.

hmm, I will need to check that out as well. Thanks for the info