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Petcock Rebuild On Kitchen Table, Need Answers First

  • Thread starter Thread starter GregM.
  • Start date Start date
G

GregM.

Guest
OK... Some of you convinced this "beginner wrencher" that this was the way to go. I've read lots of your posts the last few months and have even had a couple questions myself.
Some of you have been encouraging, "No, don't hire someone to to do this... No, don't buy a new one, you can easily rebuild it. You'll have more pride... and know more about your bike etc."
And I know you're right... I got the K&L rebuild kit for my 1980 850G fuel petcock. And I'm half way through.

I need some info and help from those who have done this rebuild on a 1980 ( and 1981... I think '82 and on used a different design) GS ??? petcock. So, in no particular order, these are things I'd like to know before I can put this back together. I REALLY only want to do this once, and I appreciate learning some of your knowledge.

There are two "gasket/wafer/rubber-ish" washer kind of things, that help seal the two bolts that hold the fuel petcock to the tank. Mine are stuck to the petcock. After I had everything disassembled, I scrubbed that one piece with lots of warm soapy water and tried to pry 'em off with my fingernail. But they're stuck.
1) What's the correct way to get them off?? And, I bet these should be replaced, they're very hard, but they didn't come in the kit. Do I see the dealer?? I gotta get these parts off my table :)

Next, there is a thin metal ring (approx 1 1/2" diameter) that sits between the faceplate and the handle/lever piece. You don't get one of these in the rebuild kit.
2) Is it supposed to be warped, or kind of bent?
It came off this way, I didn't step on it or anything :) There is a pic of this part in the Clymer book and the website micro-fiche showing the petcock, but the part doesn't look warped in the pic. It is warped like one of my old vinyl LP records from the 70's (anybody know what I'm talking about?) that was left in the car on a hot day... A warped record... that's got the same curves as this metal ring. What's up with this?

Another confusing thing about this rebuild. The back of the petcock has a plate held on by 4 little screws. There is NO pic of this side in the Clymer book or the micro-fiche, yet there's a bunch of stuff in there. That's weird, eh??
On that plate is the fitting that you attach the vacuum tube to... on the inside of the plate (where the vacuum fitting comes in) there is a kindof brass looking piece. Is this a one-way valve??
3) Is air only supposed to go one-way through this section?? Because I can suck air easily out of the back of this vac. tube port... But I can also blow a little (fairly little) air out through it (towards the inside of the petcock). How's this really supposed to work?? There is no replacement brass one-way valve (if that's what it is) in the rebuild kit. Should I have one??
Thanks for any info you can provide
 
petcock

petcock

1. rubber washers: try a little vinegar or rubbing alcohol, or warm things up with a hair dryer to soften whatever is making it adhere. Stuff called Goof Off may also work, but not sure if it would dissolve rubber. Good Off is a latex paint remover, available at hardware stores. Wicked fumes, tho, use with good ventilation.

2. Washer is I think supposed to be bent, as it supplies spring tension to hold the lever in wahtever position you turn it to.

3. I wouldn't worry about blowing air in, that won't happen when it's disconnected, only normal atmospheric pressure will be operating.

It is a one-way valve - engine vaccuum will pull it open and spring should push the valve shut again. Will need testing once reassemble.

Maybe you could cut the flat bottom on a wide tin can so as to be able to screw the petcock on with sheet metal screws, then test by sucking lightly on a tube on the the vac hose fitting. Should hold/flow liquid when operated. Insted of gasoline, try a thin relatively less stinking fluid like low-odor Varsol (also from paint section of hardware store).

Let us know how things turn out!
 
Thanks Rick... All advice is really helping me. Any other opinions are totally appreciated.

How about the gold colored spring that's on the backside of the petcock. There was a post some time ago about extending this... pulling it out to make it a little longer.

Is this a good idea???
 
spring

spring

This I don't know about, but I'm guessing it shuts the valve when vaccuum pressure shuts off, i.e. when engine is stopped.

I don't believe pulling it is really right. It never really worked in clicky-type ballpoint pens, as i recall. Maybe instead take said spring to a hardware store e.g. Home Despot where they have those cabinets of nuts, bolts, etc. See if one matches up or is a little longer.

BTW the way to reset a spring's length is with annealing and retempering, as gunsmiths do. In case want to do this, here's the process for ferrous metals:

1. Heat spring to red hot (propane plumber's torch i.e. Bernzomatic works fine)
2. Let cool slowly in air. This anneals (softens) the metal.
3. Stretch to desired length now it's soft.
4. Heat up again as before.
5. Dunk in water to cool, swishing it around so all areas cool evenly. Spring will now sproingy again, same stiffness as before but at the length you set.

If you want to make a spring stiffer, clip off a coil or coil-and-a-half after step 2. Did this with fork and shock springs on a KLR650, worked very well. Read about it in an MX magazine.
 
Thanks a ton... I really like learning HOW all this works and why it's the way it is.

I should be getting the petcock reinstalled soon... I just hope this helps my major gas odor. :)

I only had a slight leak, during my petcock test (before). Now, I hope it doesn't lose a drop all day.
 
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