1981 GS550 Petcock problem WON'T MOVE!

[CafeRookie]

1981 GS550t

The petcock on the tank will not move. I try to twist it to PRI or the position and it will not move. I've sucked on the vacuum line and can hear the diaphragm engage, but I want to be able to twist the knob/lever to bypass the vacuum line. How do I get the petcock to work? Rebuild?

[Rich82GS750TZ]

Rebuilds are iffy. Most don’t have great success with the rebuilds. I’ve only read a few account of this working. Most fail in short order. Georgefixs.com sells good factory-like new, model specific petcock s. I’ve read good things. See if they have one for your year/model. I’ll get one from them when mine quits.

When I first got my bike, it had set outside for quite a while. I could only turn the petcock lever with considerable aid of pliers (with a rag to cover the teeth). A little WD-40 helped loosen the lever a bit. It’s gotten better the longer I’ve owned it and the more I use it. Still stiff but I can now operate it with just my fingers. I’m not suggesting you go medieval on it with tools, but……. Does it work now, must be stuck in either the ON or RES position?

[bwringer]

One issue with forcing a sticky petcock, or just turning a petcock that hasn't been turned in years, is that you'll send any mung trapped in the petcock straight into the carbs.

So "my petcock is hard to turn" very often turns into "halp, there's gas overflowing all over the floor while my bike is running", and/or "halp, my engine is full of gas", as the mung props open the float needles.

[Gorminrider]

I've had a couple of sticky "original-type" petcocks. The working solution has been to make the lever longer with a bit of pipe copper pipe squeezed on to grip it. Then, i can actually turn it with gloves on while I'm riding....

Many never ever get turned when the rider is diligent refilling before RES is needed....

Taking mine apart and putting them back together didn't help for long. Lubrication doesn't seem to last. Perhaps it gets flushed out or just squeezed out. I think maybe the plastic insert sthat the lever is turning swells somehow ...you needn't take the petcock entirely apart. Loosen the chrome plate PRI/RUN/RES stamped on it (two screws) at the lever and the lever and plug is right there...to twist backnforth and oil for the moment anyways...

Perhaps someday an idea would be to adjust the pressure pushing the nylon-plastic plug in so tight but not so loose as to allow it to leak...trying to smooth it or the bore it turns in with sandpaper might easily go too far and make it leak forever. It would need a very fine wet'ndry paper and it's so easy to sand a round plastic object or hole into an oblong.... A Fine powder polish could be tried first...toothpaste maybe.

[CafeRookie]

RIght now it is stuck in the ON position. I guess that is a pretty good position for it to be stuck in! Although...maybe RES position would be better. I will try to make the lever longer so I can get more leverage when I need to turn it. I've been hesitant to apply too much pressure in case I were to break it... I've read that it can be a real pain trying to find a new working on for a good price.

[Gorminrider]

if you don't want to get too involved in a BIG FIX attempt, maybe just get a can under it to catch a bit of gas and...

loosen the screws holding the plate, dose it all with some oil from the dipstick, then "winkle" it (meaning a graduated force push- pulling, right-lefting, a little with pliers...but some tape on the pliers might save scratching...) That could help move it without breaking anything.

if you get beyond 'graduated force" aka "yarding" full strength on it or a when hammer swing seems like a good idea) you should probably stop and goto other options

[OldVet66]

Over the years I just got tired of the factory petcock problems and went for a permanent solution. I switched over to a Pingel petcock. Two things about them. (1) you have to remember to turn them off and (2) the Suzuki gas tanks are not straight where the petcock mounts so you have to make your own gasket out of nitrile gasket material at least 1/8" thick for the adapter plate, that is straight. When I made the gasket I used a leather punch slightly smaller than the mounting bolts so the gasket would seal around the mounting bolts. Don't torque the plate too tight or the soft nitrile will squeeze out like butter. Snug and not leaking is good. I used the high temp Permatex thread sealant to seal the petcock threads to the adapter plate. Z1 Enterprises has the petcock and adapter listed under your bike for about $160.00. Sounds expensive but the the quality is exceptional and I have probably wasted more on factory petcocks that only last about four years than I paid for a permanent fix.

[bwringer]

FWIW, a manual petcock would NEVER work for me. My brain just never has and never will remember to perform the ritual correctly.

Pingel does make vacuum-operated valves. Whether these can be adapted to GS tanks successfully, I don't know; there may not be space on some bikes.
http://www.pingelonline.com/prodcat/...uel-valves.asp

VERY flippin' expensive, though... well over $300 for a valve plus adapter plate.

[OldVet66]

I imagine I have a few years on you and everything was manual then when I started riding. Pushing 75. I still have to remind myself when riding the GS1000, but I turned the valve so off is always sticking straight out with that bright chrome lever. On, disappears under the tank. That's the one I have to remember to turn off. The 2021 CB500X has none of those problems, turn key, push button go.