Fuel Starvation

[007brendan]

So a couple weekends ago, I went on a roughly 200 mile round trip ride to Sacramento.  About 3/4 of the way there, I'm cruising along at about 80-85 (indicated) and I run into a pretty strong headwind, but the bike's still making power and keeping speed, so I muscle ahead anyway.  After a few minutes, the bike starts to jump and sputter like it's running out of gas, all the normal fuel starvation stuff.  The kicker though, is that I'm running with the petcock on prime, as I do every time I ride, since I first experienced the fuel starvation issue about a month after I bought the bike.

I pull over, pull the tankbag off, check the tank for gas.  Yeah, there's still gas.  I get back on, hit the starter, and it fires right up.

Long story short, can I fix this simply by going to the newer petcock?  There's one on ebay for ~$25 right now:

http://cgi.ebay.com/ebaymotors/2007-Suzuzki-GS500F-GS-500-FUEL-PETCOCK-44300C01D40J000-_W0QQcmdZViewItemQQhashZitem35ac02de93QQitemZ230519135891QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_1477wt_939

[Paulcet]

I think gsjack had a good theory on air flow across the carb vent tube causing a vacuum.... Or something like that.

[reload]

doesn't running on pri bypass the "pumping" action created by the vacuum line? if so then i would think a new petcock would do ya good.

[JAY W]

Was your tank bag pressed hard against filler cap not allowing tank to breath?

[007brendan]

I don't think so, but I guess it's possible.  The fuel delivery system on the GS sucks.