GStwin.com GS500 Message Forum

I had installed a clear vacuum line and clear line and filter to the carbs so I could keep an eye on things. Ran fine for about 2000 miles then started having to turn the petcock from run to prime when cruising at highway speeds for more than 5 minutes. I could see the clear line to the carb would empty out, when turned to prime it would start coming back & run without bucking like it was running out of gas. It was a pain in the arse but still rideable.
 Yesterday I looked back underneath at the vacuum line and noticed it was full of fuel!!! Petcock leaking internally. I do not want to pay for a new petcock yet, and don't trust a "used" petcock. I want the reserve option and don't really want to reengineer the darn thing so I took a look at it.
 Today I, clamped the fuel lines off with vice grips, took the petcock loose from the frame and found the 4 screws on the back. Removed them and found under that is a spring on the vacum side in there with a diaphragm seperating the air and fuel chamber, split around the circumference allowing fuel to get into air side. I removed a flat plastic washer from the old diaphragm, found a piece of fuel grade rubber in a kit I had, traced out the shape of the old and burnt 4 screw holes with a soldering iron. Reassembled the valve and it is running ok so far. I notice under demand, the fuel seems to keep filled in the line to the carb. Unlike it used to run about half full when it was running great.
Ok the issue I saw with this repair and will know in time. The old diaphragm had a nub that the plastic washer sat on to keep it centered. The spring is on the air side and sits snuggly in the housing on one end and rests on the plastic washer on the diaphragm as a seat to avoid direct contact & cause wear.  With my diaphragm in there it relies on the spring to hold the washer centered and there is a shoulder on the plastic that the spring slips over but its slight.

Nice repair job. Hope it holds up for you.

:cheers:

Did you happen to take pictures?  I wouldn't mind seeing what's inside that fuel selector switch without having to take mine apart....  :roll:

Sorry Kerry, I didn't.  :(

I have never took it apart but one idea might be to put a spot of RTV to hold the parts on the diaphagm they have a fuel safe version of it. Just a thought. Maybe someone has a better adhesive that would work?

Good job on the repair. will try it myself when mine stops working!

this is just great.  now i have to blow off my  date for tonite to take apart my petcock.. :roll:

I did use a little rtv blue silicone on the air side of the diaphragm to "glue" the plastic piece to the diaphragm. Also a little to "glue" the spring into the cap that is held on by screws. Pretty simple fix. Rode a little last night, seems to be ok.
Just clamp the fuel lines from the tank with vice grips, "softly", take out the mount bolt with a 10mm socket, pull the petcock out far enough to see the back and take the 4 screws out. No hoses to mess with, no gas came squirting out and it went together prettty simple. 30 minutes and I was done.

when i actually put the beverage down and stop surfing this site, i'll get to mine to have a look.  will i be able to tell if the diaphram is damaged?

Quote from: KerryDid you happen to take pictures?  I wouldn't mind seeing what's inside that fuel selector switch without having to take mine apart....  :roll:

Gee Kerry, I though you saw this previously...

Gee -- you'd think I would have remembered something like THAT!  :oops:

ok funny story..  i got off my butt to go inspect the diaphram.  well i pull the petcock off and unscrew the 4 screws.  then i pry off the cover and boom, spring shot off somewhere and i have gas squirting in my face, all down my arms, legs etc.  ya i know what ur thinking..."you idiot! u forgot to krimp the hoses shut!" ya im stupid.  so im left with a socket wrench and 10mm socket, 12 mm socket, screwdriver and thats all thats in my reach.  no ones home so im stuck holding my thumb on the petcock where the gas is coming out.  meanwhile the girl who im supposed to be on a date with is calling my fone non stop and its ringing in my pocket.  so after a min or two i realize the only thing i can do is shut the tank off.  so with my left hand on the petcock, i use my right hand to take off the plastics, unbolt the tank, and finally turn the shutoff valve.  wow that was fun. lets do it tomorrow.  

the only good thing is that i got some pics for kerry!  damnit! someone always beats me to the punch.... :x

(http://img.photobucket.com/albums/v113/weaselnoze/tempshit/dia1.jpg)
(http://img.photobucket.com/albums/v113/weaselnoze/tempshit/dia2.jpg)
(http://img.photobucket.com/albums/v113/weaselnoze/tempshit/dia3.jpg)

feel free to copy to your server.

I tell you, some people will just go the extra mile for a good photograph!  :thumb:

I didn't risk incineration for my shot. I'm a wuss.  ;)

It takes a real man to get soaked with gasoline AND have a ringing cell phone in his pocket!

I bow to your manliness! :cheers:   :lol:

Quote from: weaselnozethe only thing i can do is shut the tank off.  so with my left hand on the petcock, i use my right hand to take off the plastics, unbolt the tank, and finally turn the shutoff valve.

Impressive!  Are you ElastiGirl's little brother or something?

Thanks for the pics, all.  :thumb:

Quote from: starwaltIt takes a real man to get soaked with gasoline AND have a ringing cell phone in his pocket!

You didn't see episode 2 of MythBusters?

Quote from: RVertigoYou didn't see episode 2 of MythBusters?

Watched a few episodes, but not that one. I never believed the explosion/phone connection. I'm a ham radio operator and knew it was just plain dumb to think the phone was causal...as long as the phone didn't catch fire  :o

Wow you guys are extreme...  Just wanted to add that the plastic disc seen on the diaphragm just pops off that nub that is sticking through the center of it.

so the disc..  if the edges are at all deformed they wont seal and that would cause a malfuction right? mine looked alright but idk...