High speeds problem, please help...

[OrTahor]

Hello all.
I have a stock 99 GS500E. I love it very much.
When I hit speeds of 140kmh or so, the bike starts to act as if it is low on fuel, eventhoug the tank is full. When I hit the throttle there is a long delay, and it wabbles around. I remeved the vaccuum tube from the tank since it was broken in 3 places, but it still do this. when i go down to 100-120 is stops.
My thinking is either tthere is a problem with fuel intake, or air intake, but the shop which handles my bike (one of the best ones in israel) cant find the problem... i don tknow what to do, please help  :dunno:

Thanks,
Or.

[scratch]

I'm not sure, but I'll venture a guess here. First, I would suspect the fuel selector. If your selector has PRI (prime, gravity feed) on it turn it to that. If that doesn't fix it, you may need to replace that or get rid of it alltogether. A less drastic fix may be carburetion. Jet needles may need to be shimed or a larger main jet. This is all conjecture, as we don't know exactly what has done to your bike or if it's completely stock.

Didn't want to leave you hanging.

I hope this helps. And that all goes well.

[Kerry]

Here are a couple of old threads that may help out.  You can find LOTS more by using the Search link above and entering the term "starvation".  Best of Luck!

Fuel Starvation Issue? 1990 GS500
Fuel not reaching Carbs

[OrTahor]

OK, heres a more detailed explanation -
the bike is completly stock full faired 99' GS500E. Main problem is like I stated above when I reach high speeds the bike start to "cough" and jumps around with fuel/throttle bursts and occaisonal boom sound from the exhaust. It will eventually shut down from what seems to be fuel starvation. Now, when I lower the speeds, it returns to normal.
Also, another problem which is related is that when I have to switch to reserve (when Im low on fuel) it takes a long while till it starts pumping gas good, and for a long period it just coughs and wabbles. If I stop the bike (either cause it shut down while riding, or I choose to stop) and then resume drive it comes back to normal and I make my way to the gas station.
As far as PRI Ive thought about a vacuum problem, but it doesnt seem to be the case cause when I switch the valve upward facing the sky it doesnt help the coughing and the fuel/throttle bursts.
I really dont know what is the problem and would appreciate any help from any of you.l
Mayeb its a carb problem? or a fuel pumping problem... HELP!

Or.

[gsJack]

Do you have any rust or dirt in the gas tank that might be blocking the screen and limiting fuel flow?  Check the air cleaner too for blockage.  There is no fuel pump on the GS500, it is gravity feed.

[scratch]

Also, another problem which is related is that when I have to switch to reserve (when Im low on fuel) it takes a long while till it starts pumping gas good, and for a long period it just coughs and wabbles. If I stop the bike (either cause it shut down while riding, or I choose to stop) and then resume drive it comes back to normal and I make my way to the gas station.

Switch to PRI first to fill up the float bowls first. It'll save wear on your starter.

Kerry has posted two threads that address the other potential problems.
Petcock
Float heigth
jetting
ignition (highly doubtful, because it's non-adjustable electronic ignition.)
Gas tank not venting?
One of the coils cutting out?
vacuum balance the carburetors?