I have a question about my '94 gs 500 e. When driving on a highway, 130-140 km/h, my bike gets in trouble. It's feels like i am running out of fuel. It starts bumping, just like when you have to switch to reserve, but this happens all the time. No matter the amount of fuel in the tank. Most of the time i'm forced to stop, because the engine simply stops running. Often I hear a loud bang from the exhaust. After standing still for about a minute, I can start the engine again and drive on. I thought it had something to do with the fueltap, so i disconnected it and connected the tank directly to the carbs. Now the problem didn't occur anymore. I inspected the tap but it was ok, even the membrane. All the hoses were fine to. Any suggestions, i'm allready searching for a year now.......?

Sounds like a bad petcock.

i HAD THE SAME PROBLEM,  try just leaving it on PRIME,   life will get better

i guy at pingel petcocks said that after rejetting the bike will wnat more fuel flow wich can't be handled by the ON/Vacum position   you need to run it in the PRIME/Gravity position

just remember to switch it back to ON or RESERVE when parked (this may not be necessary but i do as good measure)

around town i just leave mine in the ON position but if I am hitting the freeway or higher speeds i reachdown and flip it up to PRIME

I had the same problem too.  I had the tank off one day and wanted to drain some of the excess fuel out (tank was too heavy) and I noticed that fuel would just trickle out of both the run and res fittings.  I replaced it with one off another tank.  I checked it and when I turned it on by the screw it poured out fast.  The screen looked clean and it didn't seem dirty but still flowed slow.

Problem went away after that.
In your case it may be the selector petcock or both.

I have K&N pods, Cobra slip-on, Jets, 150, 40, 1 washer, 3 1/5 turns out.  I feel like maybe it's starved for fuel when I really get on it and get it up close to read line for a extended period.

Paul

well thank so far, but i've tried driving with the switch on PRIME, but I still had the same problem. The tap underneath the tank works fine. I'm desperate! :x

OK if not what Pkasso said...it probably needs better venting in the tank.
Cool.
Srinath.

Quote from: PkaasoI had the same problem too.  I had the tank off one day and wanted to drain some of the excess fuel out (tank was too heavy) and I noticed that fuel would just trickle out of both the run and res fittings.  I replaced it with one off another tank.  I checked it and when I turned it on by the screw it poured out fast.  The screen looked clean and it didn't seem dirty but still flowed slow.

Problem went away after that.
In your case it may be the selector petcock or both.

I have K&N pods, Cobra slip-on, Jets, 150, 40, 1 washer, 3 1/5 turns out.  I feel like maybe it's starved for fuel when I really get on it and get it up close to read line for a extended period.

Paul

Run/Res needs a vaccum to pull fuel, thats why it just trickled out.

Me thinks he was talking about the fuel petcock up on the tank, with just a trickle out of the on and reserve lines, minus the fuel switch. Seems the tank mounted petcock can be a problem, as well as the vacuum selector switch.

I doubt very much it is the venting - that is easy to check anyway. Just try it with the filler cap cracked open.

The vacuum operated fuel selector doesn't flow enough fuel for a stock bike in a good percentage of cases. But it seems your problem might be the tank mounted on/off petcock.

Anybody can tell me where to find instruction on cleaning the petcock. I am having the exact problem as kneedown on mine GS500.

There is no problem with the venting of the tank or the petcock, because I've tried driving without fuelltap (on frame). I connected the tank with the carb directly with a hose. Now the problem was solved, so it probably has something to do with the fuelltap on the frame. On PRIME the problem occurred again, so the vacuumsystem can't be the problem. If I can't solve it, i'm going to sell it.

Quote from: kneedownOn PRIME the problem occurred again, so the vacuumsystem can't be the problem. quote]
Here the fuelltap was put back in the fuellsystem. It doesn't matter in what position the tap is, it simply doesn't run well on hi speed with the fuelltap connected.

Sell the bike. You wouldn't want to undo two bolts and 4 screws without detailed instructions.

Yeah Sell it to me, I will use it as a parts bike  :mrgreen:

Quote from: kneedownIt doesn't matter in what position the tap is, it simply doesn't run well on hi speed with the fuelltap connected.

Well, since it sounds like your mind is made up, look at this thread http://www.gstwins.com/forum/viewtopic.php?t=4228 if you want to run with no petcock at all .   Personally, I would at-least try modifying those instructions by adding a standard gravity-fed petcock from a junkyard so you would still have a "main tank" and a "reserve" (and an "off", which I would need for my bike).  Also, while you have the tank off, consider cleaning-out the screens on the in-the-tank filter unit (part #9 from http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=137946).  If that is partially-clogged, then it could be part of your trouble.  Heck, clean-out the whole tank, and add an in-line filter like the thread above suggests.  You may be having rust pains.

Thanks for all your help, but I went looking for an used petcock and replaced it with mine. Now it's running perfectly!!! No selling anymore