Petcock conumdrum!

[jonr]

You'd think it would be easy: buy petcock rebuild kit, disassemble, clean and reassemble with new parts. Of course not!

So I'm rebuilding the petcock on my 78 GS750 since small amounts of fuel were leaking from the lever when I switched from "prime" to "on". I have to say that these older petcocks are much more complicated than necessary compared to the one on my 82 GS1100. It's got the double diaphragm in the back too. So, I put everything back together after a thorough cleaning and it dribbles fuel in both the "on" and "reserve" positions (bench testing with tank on workbench with <1 gal of fuel in tank). Ugh!

Obviously it's getting air from somewhere for the fuel to flow. I double checked the double-diaphragm by removing it once more and all was well. I feared that I might have put the plastic plate that goes between the diaphragms in backwards, but it's sitting the right way. Once I had a look at it again, there's only one way it will fit if the small hole is going to line up properly. The small spring is in there too.

So, if the diaphragm is in there correctly, all snug as a bug, how in hell is this thing getting air? It didn't leak at the hose output before I did the rebuild. Anyone have a similar experience?

Help! Thanks!

J

PS. Don't want to go the pingle route. Don't want to drop the $$$ and don't want to turn my fuel on and off every time I ride.

[spyderrocs]

do what i did, leave the petcock in prime and put a inline valve in. Been like that all season so far and no problems at all.

[jonr]

I'm starting to wonder if this is happening on the front side of the petcock where the knob rotates. The older petcocks have that 4-hole gasket and if the knob does not make a good seal on the gasket, then I could see air sneaking in between the "prime" and the "on" circuits.


There was a bit of corrosion on the inside surface of the knob, but I did scrape that off with a razor. I made sure not to gouge anything, but maybe the surface is rough enough to not make a good seal.

Just a theory; any other suggestions?

-J

PS. Spiderrocs, thanks for the info, but I want to try to fix it before I make any modifications/additions.

[ptm]

I'm confused. I understand the concept of 'for fuel to come out, air has to go in to replace it or a vacuum is created and the fuel stops flowing', but I don't see how that relates to your situation. The air gets in the same way it does when the engine is running - through the vent in the filler cap. All the engine vacuum line on the petcock does is open the valve in the ON or PRI settings. The petcock leaks because some seal is not sealing.

Try tightening the four screws more. Although, too much and the lever gets hard to turn.

It's been a while since I rebuilt mine, but is it possible to rotate the 4 hole gasket to the next hole. You might be able to find a position that seals better. Or turn it over (if it seems symetrical front to back) and see if that helps.

I bought a rebuild kit for mine (K&N I think), but I ended up reusing most of the original parts becasure they worked and sealed better. I still get a little bit of residue that eventually builds up on the sides of the pecock, but it's never enough to drip. I just wipe it off with a rag once in a while when I'm cleaning the bike.

Good luck.

[jonr]

Paul,

I'll check it out per your suggestions. I wonder if that tiny o-ring that fits on the valve part of the diaphragm is not seating correctly. I might swap it out with the old one and see if that makes a difference too.

Haven't touched it since the other day due to other obligations, but there's something wrong with having two running bikes of which neither one can ride. :-(

J

[ptm]

there's something wrong with having two running bikes of which neither one can ride. :-(

J

Time to get that 3rd bike :grin:

[bwringer]

Buy a whole new petcock -- it's rarely worth the heartbreak and agony of trying to get a rebuild kit to work. As you're finding out, many of the rebuild kits contain inferior or wrong parts, and there's often corrosion on the metal parts that prevents sealing. A few folks have gotten the rebuild kits to work, but many others have had trouble.

IMHO, it's too dangerous to monkey around with. Bolt on a new petcock and forget about it for another 20 years.

CRC2 has them for decent prices, or you can order up a whole new petcock from Suzuki for just $53.72:

http://flatoutmotorcycles.com/fiche_select.asp?mfg=Suzuki&vcc=Motorcycles&year=1978&fveh=2133

[maxpower_hd]

My local Suzuki dealer told me they are no longer available, at least for a 79 GS1000L. I'm still looking for a kit now.

[maxpower_hd]

Update

I just called my local dealer and gave them the part number I looked up on the link posted by bwringer. That number has been superseeded twice but I was able to order it for $67.99. 3-5 days for delivery.

Thanks. I've already rebuilt this one once. It lasted about a year but now it went again. I'm all done with that. Especially seeing the bike isn't even mine.

[bwringer]

My local Suzuki dealer told me they are no longer available, at least for a 79 GS1000L. I'm still looking for a kit now.

"No Longer Available" from a dealer parts monkey often means "I'm too lazy to get off my butt and look it up".

There are many parts that really aren't available, but you have to at least do some digging first...

[Boondocks]

Buy a whole new petcock -- it's rarely worth the heartbreak and agony of trying to get a rebuild kit to work. As you're finding out, many of the rebuild kits contain inferior or wrong parts, and there's often corrosion on the metal parts that prevents sealing. A few folks have gotten the rebuild kits to work, but many others have had trouble.

IMHO, it's too dangerous to monkey around with. Bolt on a new petcock and forget about it for another 20 years.

CRC2 has them for decent prices, or you can order up a whole new petcock from Suzuki for just $53.72:
http://flatoutmotorcycles.com/fiche_...1978&fveh=2133

I agree with Brian. If you're trying to be thrifty, Z1 Enterprises has an aftermarket Suzuki Vacuum Petcock for $38.42.

[maxpower_hd]

I wish I had seen Boondocks post before I ordered the $68 one from Suzuki. Oh well. I just need to get this thing out of my garage before the snow flies. I have too many projects to finish.

[jimcor]

Bolt on a new petcock and forget about it for another 20 years.

Looks like the 'infamous 80' is only going about 8 or 9 years before the thing starts to have vacuum trouble.

Guess how I know...again.

[Boondocks]

Bolt on a new petcock and forget about it for another 20 years....

The original vacuum petcock on mine is still working fine with no leaks after more than 26 years. I feel that I am tempting fate by posting this, as I do when I mention that my stator and R/R are also original and performing to spec.

[jimcor]

The original vacuum petcock on mine is still working fine with no leaks after more than 26 years. I feel that I am tempting fate by posting this, as I do when I mention that my stator and R/R are also original and performing to spec.

If you're the original owner of that machine you are to be commended for keeping it in excellent condition and having VG luck. Does the '80 1100E have the slotted petcock? I know not all '80 models were cursed with the 'infamous '80' valve.