Only runs on a full tank of gas...

[holiwoodpa]

I had a problem getting my 2006 GS500f to stay running after riding for a short period of time.  It would run for about 15 min then once I came to a stop it would stall out and I couldn't get it running again until it sat for a long period of time.  So I went and bought some good gas and filled it up and it ran like a dream until I was on a steep hill!!  I'm guessing the gas floated to the back of the tank or something that and the bike wouldn't recognize that there was gas in the tank.  I coasted to flat area and tried to start it and it wouldn't. Then I put it on RES (reserve) and it started right up.  I went home and didn't have a problem with stalling the whole ride.  No hills of course! 

Is it typical for these bikes to only run on a full tank of gas!? I've only had it for 3 weeks. What could be the problem?  I have put a new air filter, oil change, spark plugs and cleaned the carbs.  Any suggestions?

K

[ivany]

Does it run when you put it on PRI? (don't leave it there for a while when the bike is off!) If so, bad petcock. Replace with a $$$ suzuki unit that'll go out in a few years, or replace with a manual petcock. I think a Honda CBX250R petcock works.

If not, try cleaning the vent in the tank cap.

[adidasguy]

Many threads on this. Possibilities are:
1. Bad fuel valve so the vacuum doesn't open it up (being on PRIME is the clue)
2. Leak in the vacuum going to the fuel valve so it isn't opening up (full tank is more weight in the fuel lines and could make the fuel valve open up easier)
3. Gunk or water in the tank - clean out old gas and refill or add some fuel conditioner. (Ethanol separates into alcohol and water which is why it is so bad - ethanol is just political and bad for engines)
4. Pinched fuel or vacuum line

[holiwoodpa]

I've never tried to ride it on PRI.  I'll try that. So, if it will ride on PRI then that means its a bad fuel petcock?

How do I clean the gas cap vent?  This might sound stupid but I don't know where the gas cap vent is. It just looks like there is a rubber seal under the cap when I lift it up.

Should I put that Seafoam stuff in tank to clean it out?

In another thread that if it starts up after stalling with the gas cap open then its the gas cap seal or something like that.

[adidasguy]

If a full tank runs on reserve and not ON, then probably your fuel line for ON is clogged or pinched and the fuel line for RESERVE is OK. Check the 2 fuel lines from the bottom of the tank to the fuel valve/petcock. (It is the same vacuum that opens it up, the lever controls whether the fuel goes in from the ON or the RESERVE hose. PRIME bypasses everything and just lets fuel flow through)

[mister]

If a full tank runs on reserve and not ON, then probably your fuel line for ON is clogged or pinched and the fuel line for RESERVE is OK. Check the 2 fuel lines from the bottom of the tank to the fuel valve/petcock. (It is the same vacuum that opens it up, the lever controls whether the fuel goes in from the ON or the RESERVE hose. PRIME bypasses everything and just lets fuel flow through)

Also check the lines leaving the petcock (on/pri/res selector). A small kink will reduce flow when you need it. If the Res and Pri lines aren't kinked, you could think it's vacuum when it isn't.

I'm guessing kinked line here seeing as you've recently done some work in areas that would effect those lines - assuming it was fine before hand.

Michael

[beRto]

plugged vent on the tank cap.