How concerned should I be?

[Guest]

I rode 500 miles yesterday. The bike ran great except at one point I was on the expressway doing about 80. All of a sudden the bike lost power and I had to pull over. I tried to get it started, but she wouldn't start up. It seemed like she was starving for fuel. I flipped the petcock to prime, waited about 30 seconds, and she fired right up. I moved the petcock back to reserve, and I didn't have a problem the rest of the day. When this happened, I had about 1/4 tank of gas, and the petcock was on reserve (I always just run on reserve).

This happend a few times last year, and I attributed it to a fuel filter the PO had onthe bike. I removed that filter and never had a problems with it again until yesterday.

Any thoughts on what would have caused that? First signs of a failing petcock?

[Baatfam]

...the petcock was on reserve (I always just run on reserve).

Any thoughts on what would have caused that? First signs of a failing petcock?

Why do you always run on reserve?
Right there I suspect you have a petcock issue if you have to do that.

[gggGary]

possible tank vent issue?
pull the petcock, and check the filter?
space worms?
Running up a hill at 80, low intake vacuum closed the petcock long enough to starve the motor?
vapor lock? Not impossible on bike, the KZ1300s were notorious for that.

[gggGary]

on the low vacuum I would replace the vacuum diaphragm or at least open it up and look at it. Low vacuum and a pin hole in the diaphragm could cause what you are describing. Quick test; remove the vacuum line at the manifold suck a vacuum and stick your tongue over it. If the vacuum doesn't hold or you taste gas, there's your problem.

[toejams1]

Why do you always run on reserve?
Right there I suspect you have a petcock issue if you have to do that.

I don't have to do that, I just do (don't really have a logical reason). It runs just fine in the "on" position.

[toejams1]

I was going uphill at 80 when the problem occured. I will try your tests to see if that is the problem. Thanks for the advice.

[Danjal]

Possible petcock problems, leak in petcock vac line, could be junk in the tank clogging the petcock filter, clogged fuel lines, clogged fuel passages in the carbs, clogged filters in the carbs, clogged or restricted fuel line, undersized fuel line, bad float height, rust in tank, tank vent hole plugged/restricted.

[Pete Logan]

Possible petcock problems, leak in petcock vac line, could be junk in the tank clogging the petcock filter, clogged fuel lines, clogged fuel passages in the carbs, clogged filters in the carbs, clogged or restricted fuel line, undersized fuel line, bad float height, rust in tank, tank vent hole plugged/restricted.

Yep - basically you have to dismantle the entire bike

[davidduarte]

you might want to check the vacuum line to the carbs, if you've never replaced it, you should be able to find vacuum line at any autoparts store, and it's cheap. Do you have rust in the tank? I hope not, but that can gum up the petcock. Remove the petcock and inspect it for any gunk (should go without saying but you should siphon the gas out of the tank first )