Has anyone had their carb bowls go dry at WOT?

[Gregory]

We were out riding (I have 1986 1150 E engine) and got out on a long straightaway with wide open throttle for a couple miles or possibly a couple minutes.

I was running about 125 when the bike bogged down and almost stopped running, until apparently, the carb bowls filled back up.

Any hunches on what this could be? Can an improper float height setting cause this to happen? Any troubleshooting tips?

 

[rphillips]

Would think if all 4 carbs going dry at same time, possibly vacuum not opening valve in pet-cock "COMPLETELY". I'd check vacuum line to see there are no leaks. Would hate to tell anybody to go ride their bike 125mph., but if under same conditions and pet-cock set to PRI. if it runs OK, you'll know the petcock is the problem.... Uh, I can't believe I said that.

 

[Buffalo Bill]

Have that problem with my 1100G.
I believe it's caused by an air bubble in the fuel line, forming where the line runs horizontal over the carbs.
The GS gravity fed fuel line system is primitive.

 

[zed1015]

Insufficient fuel supply at high rpm.
Things that need checking are fuel tank vent ( partial blockage/restricted ) , fuel tap flow, fuel line size and flow, fuel line filter for partial blockage, sediment accumulation in the float valve filters if fitted and float height check.
I'd spend a day and go through the whole lot.

 

[storm 64]

Yes...
My solution was adding fuel inlets to the outside of the 1 and 4 carburetors. The ONE central inlet was not enough to keep 1 and 4 from starving for fuel...

 

[Suzukian]

Sagging float bowls will do that. Float bowls can sag over time front the bumps in the road and gravity pushing down on them, of if they are improperly set. When you check them, shake them to make sure they have no gas inside.

 

[rphillips]

Many things sag, My wife's once rose bud tattoo is now a long stem rose tattoo. but a float bowl sagging??? I need way more explanation on that one.

 

[rphillips]

storm, any more info? I've seen a bunch of bikes, but never remember hearing of that fuel Tee and tube not serving enough fuel to the outside carbs. You've got my curiosity stirred up.

 

[bonanzadave]

You've got my curiosity stirred up.

Me too. Is there some sort of multi port manifold involved ? Seems like the petcock is only gonna pass so much fuel......

 

[Cipher]

Many things sag, My wife's once rose bud tattoo is now a long stem rose tattoo. but a float bowl sagging??? I need way more explanation on that one.

The tang might bend over time.
the spring inside the valve could rust to varying degrees as well.
the petcock diaphragm might have a hole or tear and the vacuum line might be collapsing on itself partially or even completely at high rpm.
check the fuel cap.

 

[rphillips]

Would any of these things cause a float bowl to sag? I'm still missing it.

 

[Cha5]

Don't rule out carb icing . . . .

 

[Suzukian]

It's called gravity. The Brass tangs that hold the float bowls are soft metal. Bouncing and gravity will affect their function, as the float bowls set the level of gas in the float bowl. If the floats are too low, the bike will run, but at higher speeds not have enough fuel in the float bows to sustain the drain. Float bowl setting is a major component of rebuilding carbs. If you have not done this then you have not rebuilt, or set up your carbs properly. There's also not telling what else you may have missed. It might be worth having a shop do the work.

 

[rphillips]

Now I figured it out, what you call float bowls, I call floats. To me the the float bowl is the bowl the float resides in. I set the float height to regulate the fuel level in the float bowl... Funny how terminology is different in different parts of the country... Also hard for me to imagine how more fuel could be sucked out of the float bowl, through that "tiny hole" in the main jet, faster than fuel can run in through the needle valve that has a waaay bigger opening, unless the needle isn't opening properly or some kind of obstruction up stream of the needle valve.

 

[Gregory]

I want to thank all of you for your thoughts and suggestions. Sorry it took so long to respond, I don't know why I did not get alerts for these in my email in box. I will check everything mentioned.

 

[1978GS750E]

Now I figured it out, what you call float bowls, I call floats. To me the the float bowl is the bowl the float resides in. I set the float height to regulate the fuel level in the float bowl... Funny how terminology is different in different parts of the country... Also hard for me to imagine how more fuel could be sucked out of the float bowl, through that "tiny hole" in the main jet, faster than fuel can run in through the needle valve that has a waaay bigger opening, unless the needle isn't opening properly or some kind of obstruction up stream of the needle valve.

I've never heard of the "float" (as its normally listed on a parts schematic) being called a "float bowl" before. Guess I've learned something today! Now on to the forget it part!

 

[Suzukian]

Nope, can't let that go by, I messed up. I meant to write "float in the float bowl". A leaky float will sink and let in too much gas. A float set too low will not allow the float bowl to fill up the float bowl completely and not fill the reservoir you need for those WOT moments. I apologize for not catching the mistake I posted. The way I worded it made no sense. Floats will sag because the tang does bend after a while on some carbs, mostly on older bikes. Bouncing and gravity takes it toll,and then it floats up too high, shutting the needle valve with the float bowls not being full. Hope that clears it up what I was trying to post. .