Ok everyone im new to riding!!! Just got a great deal on a 92 gs500 and since im unable to ride at the moment (broken collar bone) i let a buddy test ride it for me. Hes only ever dealt with dirtbikes and quads, so when he went to start he used prime on the petcock. We assume it sat on it too long and flooded the carbs leaking gas from the air box.
So my question is how does the prime setting work? When do i use it? And for how long?

Thanks for any help!!!

PRIME takes gas from the reserve level in your tank. It bypasses the vacuum valve. Main use is to refill the carbs after they have been drained or you completely ran out of gas. PRIME will let gas flow to the carbs with the engine off. If the carb floats are working right, it will not flood the engine as the carb floats are what actually controls fuel flow into the carbs. PRIME lets fuel from the tank in the absence of the vacuum from the engine - so for refilling carb bowls.

ON - always leave it there. You don't need PRIME once the bike is running and there is gas in the carbs. That is, PRIME is only needed if the carbs are empty. ON is where you leave it all the time.

RES - reserve, It takes gas from the lower part of the tank. You have a 4.1 gallon tank of which about 1 gallon is reserve. once you calculate your average mileage, you'll know how far you can go on reserve. Probably 40 miles minimum or up to 60.

If you don't have one, get a Haynes or Clymer manual. I prefer Haynes. The front of each is a basic owners manual with descriptions of all controls - including fuel petcock - and the basic maintenance. Chapters 2 and on are the detailed service information.

Thanks adidasguy. He had a feeling it was the float but like i said were new to real bikes. Were gonna clean up the carbs today and hopefully have no issues. Someone did junk work and didnt even have true fuel lines from the tank to petcock. So im replacing those as well. I appriciate the help buddy.

 I was under the impression that leaving it in prime can in fact bypass your float needles if left for long enough.

If the floats & needles are not up to snuff, then there COULD be a slow trickle. If in ON or RES, then fuel is cut off so only what's in the fuel line from the petcock to the carbs will flow.

So yes, if in ON or PRIME you can't flood carbs. If needles are working correctly, then PRIME will not flood them.

After all, when you are running, fuel is free flowing to the carbs and  the needles control the flow. If needles are not operating correctly and controlling the flow of gas into the carbs, they will flood and one carb could run very rich as a result.

I thought if you flooded your carbs then some gas might get into your oil.

Might want to see if oil smells like gas?

Graham 

I had a leaking needle valve once after got my 02 GS and I had parked my old 97 GS and left it in prime on the center stand.  I wanted to use the 97 later on and pulled the dip stick first to see how much oil was in it and it was way overfull with an extra quart of gas in the oil.  Others here have reported gas leaking into the airbox and out the drain tube so I guess it could go either way depending how it's parked.

We had it strapped up in a truck bed to get it to my area, about an hour drive. The gas was in the airbox  leaking out the drain tube like gsjack said. I did check the oil and it seems clean to me but ill double check that. Im in the middle of cleaning the carbs to get her running right.

If in PRIME and riding in a truck, the vibration will cause the floats to bounce around and gas will flood the carbs. Riding in the back of a truck is not a normal situation - such as being parked and not touched.

I cant remember what it was set on while we drove home. But for now im playing better safe than sorry. It seems like maybe somethings sticking anyway so im playing with it. Besides i cant ride it for a while anyway so why not trouble shoot and learn. Either way i see what youre talking about adidasguy. I appriciate everyones help with all this.