Petcock Settings and Clogged Carbs

[25knots]

Hey guys, I've got something of a noobie rider trouble-shooting question for you.  I've got a Suzuki GS500 (my first bike) with 19,000 miles and which generally runs well.  Twice, however, the engine has shut down on the road from what sounds and feels like a lack of gas getting to the engine because of a clog in the fuel system, probably in the carbeurators.  The bike has the same stuttering, halting feeling it gets if I'm starting to run low on gas (though in these cases there's been plenty of fuel in the tank--i checked). Both times, I've been able to solve the problem with a carb cleaning agent from the gas station, so its been a cheap fix, but I'd still like to know what's causing the problem in the first place because holding up traffic while I thrash around with my ignition, petcock and choke is frustrating and just plain .

And here's some additional info that I'm pretty sure is related to the problem.  Both times this as happened its been right after I ran my tank almost to empty.  And I can't say this for sure, but I think in both situations I had forgotten to switch the petcock off of "Reserve" and back to its normal, full gas tank setting.   So what I think is happening is something like this: running the tank to the bottom means the fuel system is starting suck in some sediment that normally sits too low in the tank to get sucked down the higher fuel line intake of the "normal" petcock setting.  But what I can't figure out, then, is why the engine doesn't start to hiccup when I'm running on reserve.  The problem only really starts once I fill up the tank and forget to switch the petcock back to normal.   If there is sediment getting sucked down the reserve fuel line, why doesn't the problem start as soon as I switch over to "reserve" setting?  

The only answer I can come up with is that what happens is that refueling an empty tank means that fuel is hitting the very bottom of the tank and stirring up more sediment than it would if, say, I was filling up a tank that wasn't completely empty.  But wouldn't the sediment settle back down eventually?  Both times I've gotten stuck, the bike had sat overnight before I took it out for a ride; that is to say, the problem didn't start right after fueling up the empty tank, though I only had about a quarter mile ride from the gas station to where the bike got parked for the night.  So the clog might have started right after refueling but not had time to starve the engine before I got home.  

I hope that all make sense.  I think the easy solution is just to be more vigilant about switching the petcock back to normal after running low, but I'd still like to understand what's going on.

I should also mention that the tank appears white on the inside, which I think means that its been refinished (I'm at least the third owner).  The tank also sustained a dent which was professionally repaired by a reputable shop in town.  I have a feeling that's when the inside was refinished.

Thanks in advance for your thoughts.

[Sport-Touring]

[DaisyCutter]

I rarely if ever touch a petcock.  I also live in Arizona where I ride regularly year round.


I'd try filling up the tank before I needed "reserve" and never touching the petcock again.


Also, in my experience a fuel treatment won't clear sediment.  It may dissolve gummed up fuel, it may clear out some moisture, but I can't imagine it's going to do anything to what amounts to little rocks.

Possibly check your fuel tank vent.?.

[25knots]

Thanks DaisyCutter.  That's good advice about avoiding the Petcock.  I'm still getting used to my bike and its hard to sometimes judge fuel consumption.  Sometimes I can make it 150 miles on a tank; other times I don't get past 90.  And, unfortunately, the bike doesn't have a fuel gauge.  I try to fill it before things get too low, but I've been caught out in the country a couple times and had to go to reserve.

[25knots]

I did check the fuel tank vent and its fine.

I think it might be gummed up fuel, or perhaps air in the system.  The Carb treatment cleared it up both times so that would make the most sense.

[bikerfish1100]

there's no way to get "air" into the fuel supply system. at least not while still getting a sufficient supply of gas.

take the tank off, remove the petcocks. clean the intake screens, see what ya got. "sediment" should be minimal, at worst. water is a more likely culprit. consider adding an inline fuel filter between petcock and carbs, and put the bike on a diet of Chevron Fuel Cleaner every few tanks.

[bomber]

there's no way to get "air" into the fule supply system. at least not while still getting a sufficient supply of gas.

take the tank off, remove the petcocks. clean the intake screens, see what ya got. "sediment" should be minimal, at worst. water is a more likely culprit. consider adding an inline fuel filter between petcock and carbs, and put the bike on a diet of Chevron Fuel Cleaner every few tanks.

^this is a good start -- avoiding the use of the petcock is simply avoiding the problem -- if there IS crud in the tank, it will continue to accumulate, and you'll have to avoid riding . . . . .

clean the petcocks (not comlicated, and will increase your confindence to tackle other projects), and install a fuel filter.

you'll be a better wrench, and your bike will be a better scoot, to boot.

[ConPilot1]

If you do install an inline fuel filter, make sure it's got sufficient flow to feed your carbs or you'll wind up with a fuel starvation issue there too.
check the routing of all your gas lines, make sure nothing is pinched or kinked, and make sure the tank vents are clear as well as somebody mentioned earlier.

[Scratch33]

consider adding an inline fuel filter between petcock and carbs

^this.  Have done that with both my SV650 and fussy 1st gen FZ1.

[Kneescrubber]

...Sometimes I can make it 150 miles on a tank; other times I don't get past 90...

A little heavy on the right wrist?