Carbs starve when riding on cobblestone roads

[Guest]

I am curious about the fact that when I have to ride the bike on irregular roads, such as cobblestone streets (Antigua Guatemala) my GS seems to run out of gasoline. I have to stop for a half a minute for the bowls to fill up again, in order to continue for a block or so, and repeat the procedure. The Carb floats are well calibrated, yet, it seems like, the vibration affects the gas flow in this conditions. Any suggestions? Other bikes don't seem to suffer the same ailment.

[Richsuz]

Good morning.

That is a new one on me. After thinking a bit I am leaning toward a vacuum problem.

Perhaps the vacuum line to the petcock as a leak and vibrations make it open to the outside air then the petcock closes the fuel.

Have you tried ridding the same streets with the valve on prime?

The Gurus might have more ideas on the subject.

DP

hmm, no I have not. I have experience this now and then, since I can't ride, my wife took my bike out and commented on the experience, hence my asking. I will check on that next time.

[Steve]

How is the suspension set up? If it is rather stiff, the whole bike will be jostling around, putting little tiny whitecaps in the float bowls.

Change the fork oil, put in some fresh 10w to smoothe things up a bit. Make sure you have proper springs and dampers on the rear. A smoother ride works better for the bike, too, not just for you.

.

[Richsuz]

How is the suspension set up? If it is rather stiff, the whole bike will be jostling around, putting little tiny whitecaps in the float bowls. Don't understand the whitecap coment. The ride is is stiff. Front is fine, rear has MDI shocks.

Change the fork oil, put in some fresh 10w to smoothe things up a bit. Make sure you have proper springs and dampers on the rear. A smoother ride works better for the bike, too, not just for you..

I hear you. Just can't seem to afford $250 plus, on shocks at the moment. I was told to put the old springs on the MDI shocks to help the situation, unfortunately my old shocks went in the trash.

[ChicagoBob]

Clearly a fuel starvation issue. Your fuel line could be kinked or compressed, the vacuum line from the petcock could be loose or broken, the fuel screen could be loose inside the tank, or the vent could be partially blocked.

The good news is that a problem like this is usually cured by the simplest possible (and therefore most satisfying) solution.

My first advice would be to stay off cobblestones. I don't even like to walk on them.

[Richsuz]

Clearly a fuel starvation issue. Your fuel line could be kinked or compressed, the vacuum line from the petcock could be loose or broken, the fuel screen could be loose inside the tank, or the vent could be partially blocked.

The good news is that a problem like this is usually cured by the simplest possible (and therefore most satisfying) solution.

My first advice would be to stay off cobblestones. I don't even like to walk on them.

We'll check all of it. But there are not manifestations of starvation on good roads. If vaccum was compromised, it should show at hi rpm, should it not?

Living in an area where there are a lot of hispanic colonial sites, Antigua being a world heritage site as declared by UNESCO, you can't avoid cobblestone roads, it adds to the experience....

[ChicagoBob]

Are you using a vacuum petcock? How do the bowls fill again with the engine off?

[Richsuz]

Yes, using the vaccum petcock. I just stop the bike from jiggling for about 20 secs. If the bike actually shuts off, I prime it.

[Steve]

I Don't understand the whitecap coment.

Think ... "ocean surf" ... "waves" ... "WHITECAPS".

Waves in the float bowls could wreak havoc on the actual fuel level. The floats might be riding on the peaks of the waves, but the actual level might be low enough to starve the engine.

Your MDI shocks might just be stiff enough to cause the carbs to jostle enough to cause the 'waves'. Have you noticed any difference if the bike is loaded down vs just you riding solo?

.

[Richsuz]

`Like surfing! Floats, "floating on the crests of the waves, got it...
It is hard to judge "loaded down". I weigh 140 lbs, 155 fully geared!?!? When I traveled to Mex with Tank bag and saddlebags, Probably only added another 70 lbs. So Max. total load the 650gl ever sees is about 225 lbs.

[chef1366]

Replace Petcock and Lines
Set float heigth to suggested level
Ride