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Pet-cock is more like a pet-rock

  • Thread starter Thread starter Skiprrrdog
  • Start date Start date
S

Skiprrrdog

Guest
As God is my witness, I finally learned my lesson; never, ever, ever, ever again will I waste precious time and money trying to rebuild any of these crap UJM 1980's petcocks.

I recently acquired a 1986 GS550ES and it had a couple of fuel leaks, one of which was a high float level, the other, the petcock. Actually, if it were not for the fact that this bike has the petcock with the round plastic knob that fits flush in the sidecover, I would have tossed it, and bought anything that fit (46mm bolt spread) So anyway, I tried a K&L rebuild kit...cue the laugh track. So now I am waiting God knows how long for Partzilla to deliver an $80.00 OEM model.

Are there any other choices for petcocks for these bikes? I *really* want to keep the plastics on it!

Thanks!
 
I'm 50% on rebuilding petcocks. Sometimes you just have to bite the bullet. But I always try to rebuild first. Usually they leak from the selector knob joint and a $5 gasket fixes it. Well sometimes. If fuel won't flow or doesn't stop flowing that's another issue. Disassemble and soak overnight in white vinegar, follow up with tooth brushes and brake cleaner and if the diaphragm is not punctured, I'll replace the O-ring on the plunger and give it a try. As I said about half the time I can repair, half the time I have to buy new.
 
Yeah, I know... I feel better now :) I am at about the same percentage... was just bummed I could not *ride*!

Maybe Ill try that with the one I put the K&L kit on. Take it off again, soak it in vinegar, then give it a run thru the ultrasonic. Its weird, but both before and after I rebuilt it, the gas would flow on prime, but when I hooked a mityvac up to vac port, nothing, not on 'on' or 'reserve'. I look at that petcock and it is not completely obvious how the vacuum works; is there something in the petcock, in between the nipple and the little round area with holes in it?
 
Not sure what model you have. Has a lever or just the screw head.
If the lever type you can pull the lever off and see the inside behind that gasket with 5 holes in it. That is the plunger you should see moving when you apply vacuum with your mighty vac. If it doesn't move then I have to ask does it hold vacuum? you know pump it up to about 5 inches of vacuum, on the gauge, and see if it holds vacuum. A slight bit of "leak down" is tolerable. Like you pump it up to about 20 and you can see it loosing vacuum and it's all gone in a few seconds that's too much. But pump it up and see the needle drop 1 or 2 inches in 20 or 30 seconds that's ok. If it bleeds down your diaphragm has a hole or is torn. If it holds then the plunger is stuck and overnight dip in vinegar will clean it up. Be extrememly careful when removing the back side that has the diaphragm. It will tear easily and then must be replaced. I've used heat from my heat gun, after the screws are out, to help loosen it up.
 
I hope my description is clear. forgot to mention that if the plunger is stuck DON'T FORCE IT by pulling on the diaphragm. With the lever off you can push the plunger out (through the center hole of the 5 hole gasket) when the lever is off. Once you have the diaphragm, with the plunger attached, removed you'll see a small O-ring on the end of that plunger. You should replace it.

Like I said soak overnight in vinegar and use a tooth brush and brake cleaner to clean the internals. A rag wrapped on a small screw driver will help clean out the passage where the plunger rides. When you have it clean put some Vaseline on the o-ring and re-assemble.
 
about the same score here...replacing rubber o-ring etc.
In the end, however, everything wears out.
and I think that includes the metal bore the plunger+o ring moves in...a bit of oxide stuck to the oring or whatever...the plunger gets sticky in the bore. Polishing it enlarges the bore-also problematic. A bit like doing an engine or Brake piston. If the bore gets a smidgeon too big, the o-ring will not seal...etcetc.
The spring is important too. (the one that holds plunger in versus vacuum). I suspect these should be measured for length versus a new one (like a clutch spring) to see if they've "lost it" too.
Stretching them to try and make the petcock function (ie:against a sticky plunger) is bad science in my experience!
 
Yours is by far my favourite thread title over the last five years...

I hear you on the petcock front. I ran into problems with the one on my 83 550es, and couldn't find anything to directly match up and fit. At least your operating handle is flush, and isn't hidden behind the little fuel door, which is kitschy-cool and all, but a royal PITA.

I hope the petcock they send actually works for your model year, because the part number that superceded the one for the '83 did not work for me.
 
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