What Happened? And what do I look for next time?

[mrquadriga]

Traveling down the Freeway last night after dark, about 80 mph making a pass, all of a sudden the motor just shut down. Like it was out of fuel. It couldn't have been as I had just filled up 15 miles earlier. I coasted to the side of the highway, tried to get it started a couple of times, no go. Many years earlier, automobiles used to have a problem that we called around here at least as "vapor lock". Having had that problem in many of the junkers I've owned in my life, that's really what it felt like to me. The motor would crank just fine, it just wouldn't start. I'd try it, let it sit for a few minutes, try again, let it sit, etc. Finally, it started to "catch" like it needed choking and after completely choking it and manipulating the throttle, it started. For a few seconds, it seemed like it was going to die again but then just cleared right up and began revving quite rapidly while on choke! I shut the choke down, it returned to its' normal idling pattern and after I let it run for a few minutes, I jumped on and rode the rest of the way home with no problems. Conditions last night were as follows, clear, 50-55 degrees Farenheit, low humidity and this happened almost 100 miles into a 150 mile trip. I got home, let it cool down for a while, went out and it started right off. This morning it started again right off. What the heck happened? Not something as silly as "Bad Gas"or could it be? I'm stumped but eagerly waiting your opinions/answers. Sorry for the long post but I wanted to give as much details as possible because being on the side of the road in a bad part of the county after dark is a bit spooky and one I'd like to avoid from now on. On a side note, no one even slowed down to see if I was okay for the half hour I was there...so much for Minnesota nice. Thanks for listening .....Pete- '80GS1100L

P.S. I learned a lesson as well last night, a small flashlight is not a bad thing to have if riding after dark...

[Scud]

It could have been that the vent in the cap of your tank was malfuctioning and then it freed up somehow. Just a thought.

Scud

[back_online]

On one of my previous GS's I had a vacuum problem and when I turned the petcock to reserve (and vacuum wasn't needed to hold open the diaphram) it ran, not perfectly but did run. Found the rubber hose cracked.

My buddy had 550 GS that if ran at full(or almost) throttle for any extended period it would sputter and die. If left for a 10 of 15 min, it would return to it's normal self. I suspected the floats / needles would let the bowls run dry and either get stuck, or a similar lack of vacuum problem as above. He sold it before we determined the cause.

Best of luck,
I an in North of Minneapolis, if you need help with a carb rebuild.

[earlfor]

At 80 mph, you would require a high fuel flow rate. In a pass, you probably were close to, or at wide open throttle. I will guess you ran it out of fuel. I will also guess that when you went to restart, you did not switch to prime to fill the float bowls so consequently the petcock valve would only open as you were cranking. Meaning, fuel would only flow to refill the float bowls during the time you were cranking the engine and vacuum was available to operate the petcock diaphram. If you have an inline fuel filter installed, I would suspect that as the fault. I dont use an inline filter for that reason. Next possibility, a cracked vacuum hose/line on the petcock. I have also had the problem be sediment in the fuel tank. At low throttle settings, enough fuel would flow through the petcock screen. As fuel requirements increased, more and more sediment was pulled onto the screen, blocking flow. Eventually, it reached a point where fuel suction/flow would pull enough sediment onto the screen that there was not sufficient flow for engine requirements. Letting the bike sit for 10 minutes would let the sediment fall free of the filter screen and the bike would run normally.

Earl

[Anonymous]

Try removing the carburetor vent lines.

http://www.thegsresources.com/_forum/viewtopic.php?t=36295