I'm new here, if you're reading this thank you for taking the time to do so.

I bought an 04 GS500F about two months ago.  It's my first bike.  I should have done this a long time ago!

My issue is fuel leaking from apparently both carbs.  But she ONLY does this when sitting for several hours.  I have zero driveability issues.  I've taken the carbs off and inspected the floats and needles.  Both look fine.  I also checked the vacuum system and vent tubes, everything mounted on the carb anyway.  I even checked the float height today.  Everything looks good.

Unfortunately I can't even tell exactly where the fuel is actually coming from.  It isn't coming from a vent that I can tell.  But the bottom third of both carbs is soaking wet after the bike sits for say 3 hrs or more.  Also of note, I have been checking the oil level regularly with no change so far. 

After reading another recent thread here I'd like to share a theory I have.  If my frame mounted petcock isn't working properly (allowing fuel to bypass it when there is no vacuum present) would the pressure of the fuel in the tank above be enough to force the needles open?

That's just a theory......  All advice is definitely welcome at this point.

Jason

I've never heard of a bad petcock forcing needles open, but if the carbs are overflowing at all it's a guaranteed bad petcock.

It doesn't take much for the needles to foul, you might want to really clean the seats out and try them again.

Could also be a bowl gasket failure.

Watcher- As frustrated as I am I'm thinking about rebuilding the lower half of each carb.  I think it's really odd that both needles or even bowl gaskets would fail at the same time though. 

I've been looking online, I haven't found that frame mounted petcock yet.  If I can find one I may just order it too.

Quote from: Trbdsl96 on November 07, 2016, 04:20:27 AM
I think it's really odd that both needles or even bowl gaskets would fail at the same time though. 

I've been looking online, I haven't found that frame mounted petcock yet.  If I can find one I may just order it too.

Well, both needles are exposed to the same fuel for the same duration.  It stands to reason both would wear out at a similar time.  Fuel isn't exactly "clean" either.  Maybe at the refinery it is, but by the time it gets tanked, hauled, transferred, stored, pumped, stored again, then combusted, it can pick up a lot of crap.  There's a reason fuel filters are a thing...

But there could be another explanation.  The carbs are connected both at the fuel inlet and overflow.  A leak at either of these locations could result in the fuel traversing carbs.

My first thought would be to make sure the petcock is set properly (ON or RES rather than PRI) but it sounds like you've already looked at that. If fuel is getting to the carbs while the bike is not running, I would think it has to be petcock failure. 

Hi Trbdsl96, welcome to the forum. Sorry to hear about your troubles!!

I did a search on ebay and didn't find much (can dive into it more later on when I have a chance) but I did pull up the motosport site to see if the frame petcock was available... it's #1 on the list and in the diagram. Kinda pricey    but at least you'd know you are getting a new OEM part.

http://www.motosport.com/motorcycle/oem-parts/suzuki/2004/gs500f/fuel-c o c k

(Bah... had to space the last bit of letters there cuz of the forum's filter!! It automatically changed it and then the link wouldn't work LOL)
Could always check the other sites like bikebandit and revzilla but I always liked motosport because of the 20-25% off OEM parts.

Good luck!!!

Thank you Watcher.  You're correct of course.  I'm going to try the petcock first but I will be rebuilding my carbs in the near future.

Quote from: qcbaker on November 07, 2016, 06:37:04 AM
My first thought would be to make sure the petcock is set properly (ON or RES rather than PRI) but it sounds like you've already looked at that. If fuel is getting to the carbs while the bike is not running, I would think it has to be petcock failure. 

The petcock is definitely set right.  Thanks for the reassurance that the petcock is failing though.

Quote from: ShowBizWolf on November 07, 2016, 02:41:38 PM
Hi Trbdsl96, welcome to the forum. Sorry to hear about your troubles!!

I did a search on ebay and didn't find much (can dive into it more later on when I have a chance) but I did pull up the motosport site to see if the frame petcock was available... it's #1 on the list and in the diagram. Kinda pricey    but at least you'd know you are getting a new OEM part.

http://www.motosport.com/motorcycle/oem-parts/suzuki/2004/gs500f/fuel-c o c k

(Bah... had to space the last bit of letters there cuz of the forum's filter!! It automatically changed it and then the link wouldn't work LOL)
Could always check the other sites like bikebandit and revzilla but I always liked motosport because of the 20-25% off OEM parts.

Good luck!!!

Thank you sir!!!  I couldn't find anything about this part.  Now I have a part number!

Quote from: Trbdsl96 on November 08, 2016, 12:24:58 AM
I'm going to try the petcock first but I will be rebuilding my carbs in the near future.

Well, these leaks happen because of two faults or don't happen at all.  Good needles/seats/floats/etc can hide a bad petcock, a good petcock won't allow for an overflow situation and thus hides potential leaks/faults

For a quick fix just get an on/off ball valve from an auto parts store and put it in line below the petcock.

I'm going to fix it one way or another......  I bit the bullet and ordered a new OEM petcock and kits to rebuild the carbs.