3 weeks ago I bought myself a gs500 ( and was extremely pleased with myself ).
After the first week of riding ( i ride 35 miles to work each day on a motorway ), I realised there was corrosion in the tank and that the resulting water was getting through to the carbs and blocking them.  I sorted this by clearing the tank, draining the carbs and fitting a fuel filter.
But now I have a problem with the mixture being too rich ( i think ) and the bike likes to cut out after every 10 miles or so ( at which point i have to sit for a min. or two before it'll run again.  If i use the choke, it automatically cuts out immediately.

I've had the top apart to see if there was anything obvious and have changed the air filter ( no difference ) and have noticed that the right-hand carb's diaphragm is too larg to sit in its groove properly but the air gate valve can still move up and down freely.
I am really stuck given that my knowledge is very limited, but would like to fix this myself if poss.
Others have speculated that the carbs aren't balanced or timed properly but i wouldn't know how to sort this either...
Anyone with any ideas, PLEASE let me know asap

Thank you

Glyn

Sounds suspiciously like a petcock issue. Try riding for a bit with the selector on PRI and see if it still does it. Vacuum operated petcocks are notorious for developing leaks.

If the bike is running and then dies and won't restart, it would have to be VERY rich to do this. Rich enough that you would use an entire tank of fuel in nothing flat.

I run it on PRI most of the time ( maybe this could be part of the problem ) I'm getting about the same mileage out of it as i do from my car at the moment !
I'm not afraid to get my hands dirty but i have an embarassingly little amount of knowledge of bikes as i only passed my full test 4 weeks ago, so how do i alter the mixture ?....

Maybe the narrow vacuum pipe is blocked.....
I cleared the others when i cleared the tank of corrosion but not the vacuum pipe..............
worth a go.....

I had the same problem.  I could see my clear fuel filter would go empty when running hard for a little while.  I replaced my tank and when I tried to drain the left-over fuel in the old tank, I noticed a very small amount of fuel coming out of both the on and reserve tube right out of the tank without any hoses connected.  It took forever to drain the tank.

I checked the fuel that would run out of the new tank and found it flowed strong and forceful.  Like a 10 to 1 difference.  I think the valve in the tank was just dirty, faulty or something.

I haven't had a problem since.  First extra cash I get will go toward the Pingle petcock.  You don't have the luxury of a reserve warning but that's the trade off it seems.

I seem to remember reading a cheaper method of using a riding mower inline valve or somthing. I'll have to research around here unless someone remembers.

Paul

what is the difference between 'pri' and 'on' ?

Quote from: newgs500what is the difference between 'pri' and 'on' ?

"Pri" allows fuel to flow down to the carbs without the need for a vacuum draw from the carbs.  "On" required the carbs to create a vacuum to pull fuel down to them.  When I first bought my bike the original owner said he always ran the bike on reserve ("res").  When I tried to run it on "on" it would seem to die all the time (probably because that circuit hadn't been used in so long that it got gunked up).  Eventually the "on" circuit finally started working correctly (after I ran the gas completely out a couple times on accident).  If I were you I would try running the bike on "on" or "res" instead of "pri".  You might be getting too much fuel to the carbs on pri and it could be flooding it out.

John L.

Quote from: PkaasoI seem to remember reading a cheaper method of using a riding mower inline valve or somthing. I'll have to research around here unless someone remembers.

See the picture about 1/3 of the way down the old thread Need fuel valve

And if anyone tries it, let us know the result.  (Von Vester!  Did you try it yet?)

Quote from: newgs500what is the difference between 'pri' and 'on' ?

In addition to the other explaination, in PRI if you happen to have a stuck flaot in the carbs, all of the fuel in the tank will overflow through the carbs and onto the ground.  Not convenient of very safe.  

ON is to be used to regular operation of the bike.  PRI is for when you run out of gasa dn re-fill the tank.  Put on PRI for a couple of seconds to get fuel back to the carbs.  Then put back to ON.

Kerry: I broke down and paid $60 for a new Suzuki GS500 fuel valve, so I didn't try the lawn mower fuel valve alternative. My old fuel valve flows fuel fine but has no selection capability. You get a free flow from both 'Alt' and 'On' hoses if you remove the cone from the inside of the valve. A simple porcedure.

To answer the original 'rich mixture' problem posed on this message, I had a similar problem. One cylinder on my GS was running very rich. The right cylinder spark plug would get carbon fouled so bad that the bike would hardly run (carbon fouling is caused by a rich mixture). I opened the right cylinder carburetor and discovered that the jet needle spring seat was missing (note: SPRING SEAT not spring). This prevented the spring from closing the jet needle whenever the engine was returned to idle thus making the mixture very rich at low speeds. The spring seat is only held in place by the spring so as soon as you remove the diaphragm cover the spring and spring seat fall out. It is small and very easy to over look.

You can easily check if the spring seat is missing without removing the carburetors. Remove the gas tank, remove the diaphragm cover from the suspect carb, lift the spring out and look for a round plastic washer on top of the jet needle (there is also a small plastic bead under the jet needle so don't get confused). The plastic washer is your spring seat. If that is missing you have major mixture issues.

Hope this helps. Ride safe.