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Petcock Rebuild

  • Thread starter Thread starter gs850cmc
  • Start date Start date
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gs850cmc

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Hello,

Looking for some advise on a GS850G (1980 45k miles)petcock rebuild. The bike was running real well following a complete carb tear down and rebuild followed by a sync and air screw adjustment (max idle technique). My trouble started when I decided to rebuild the petcock on GP's since it is so old. So I bought the kit and it seems complete with a diaphram, gasket and orings. The job was fairly simple except that now my nicely rebuilt valve leaks when in the on position and starts draining out of the carb, I noticed this quickly enough so that fuel did not get in the crank case. The one thing I noticed when I took apart the valve is that the part of the diaphram with the small o-ring on it seemed to be pressed into its seat, whereas when I rebuilt it I did not or was not able to press this part in until it locked down like the original. Is anyone familiar with rebuilding these valves and am I clear enough on what I have tried to describe. Could pressing firmly down on the diaphram shaft be my issue. Lastly I was very surprised to find that my fuel valve was very clean with rubber and diaphram in good condition...should have left it alone!

Thanks for the help
 
Its a wast of time, excercise in futility, simply buy a new one for 50ish bucks and dont worry about it for another 20 years...
 
Don't buy a new one untill you try this. Remove the diaphram from the valve. file about 10-15 thousands off the end of the tapered end of the aluminum spud attatched to the diaphram.
The problem is the spud is too long and the little brass spring thingie in the valve which activates the prime function caused the valve to stay open a bit. Be sure that the seat for the O ring is clean and not pitted as well. After fileing and reassembly of the valve test it before installing the tank on the bike.
V
 
TheCafeKid said:
Its a wast of time, excercise in futility, simply buy a new one for 50ish bucks and dont worry about it for another 20 years...
Click to expand...

Yeah, what he said.

I've said it many times, and I'll say it again -- the petcock is a valve that controls the flow of a highly explosive substance six inches from your crotch. This is not the place to cheap out.

The rebuild kits are low-quality crap, and the petcocks often have internal corrosion that makes them impossible to rebuild.
 
It's been posted here before that some petcock rebuilds don't go well. I asked that question and was hit with, Don't get a new one. Ya gotta figure if it went that long before it would stand to reason it's worth the expense of a new one. Alot of folks here are of that opinion and from what I've learned from them I would take the advice.
 
Thanks for the quick replies, I will go ahead and get a new valve, but in the meantime I'm still curious why the old one has this problem. The rebuild parts did look pretty good to me, although I have no idea how well they will hold up under use.
 
I've rebuild petcocks before with fine results assuming there is not any corrosion on the petcock casting. The problem I've noticed is that most of the rebuild kits don't seem to have all the proper O-rings to do the job on the Suzuki petcocks.

The diapharagm should have a spring behind it so that small O-ring is pressed into the cavity on the petcock body. Do you have the spring? Also, take a good look at the petcock casting in the location where the small O-ring seats. The metal surface needs to be smooth and free of corrosion.
 
Get a Pingle petcock and adapter block on , off & rev no problems. I went thru the rebuild deal with same problems glad I made the switch.
 
Rebuild kits.

Rebuild kits.

Only problem I had with a rebuilt petcock was when a piece of crud got in the way and let it drain again. The K&L rebuild kits are fine if your sure you can get the right one. If you have fuel getting past the diaphram into the #2 carb vacume line then something is wrong with the diaphram. Send the kit back and get another one. If you don't want to worry about crud then get a pinguel. Then you'll have to worry about remembering to shut it off and weather or not all four needle valves are working.
 
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Personally, I think it's equally crazy to overreact and install a Pingel instead of a new OEM petcock. More expensive, too.

I have a fairly decent brain and memory, but I know for a fact that engine vacuum is far more reliable at remembering to turn the petcock off and on than I am.

Nothing lasts forever. The OEM petcocks "only" last around 20 - 25 years. I don't see why so many people are convinced this is so horrible.

On another note, please keep in mind that the OEM needle valves and seats are not designed or capable of holding back a tankful of gas indefinitely, even if they're in perfect condition. Many people seem to forget this -- even if everything is perfect, forget to shut off your Pingel once and your engine can go boom the next morning.

But what the hell -- it's your bike. Do what you want. :D
 
Yanno...Brian, just to PROVE it to these people, after the WV rally im going to put my little "experiment" together. It will consist of a pexiglass box, complete with fuel inlet, needle valve, float assembly, etc. Then im going to MEASURE the distance from a stock carb to the petcock, so no one can scream OH there was simply TOO MUCH pressure on it, not a real situation. Then im going to hook a temp tank up, with gas in it obviously, and im going to let it sit, and sit and sit, and each day i will record HOW MUCH fuel has gotten past those perfectly good needle valves and into the plexiglass box...


Hrmmmm.....Maybe not...that sounds like a lot of work. But, it would SHOW people that yes, THEY WILL LEAK DAMNIT!!!
 
I took the thing apart again and what I noticed is that the part of the diaphram that has the small o-ring on it is just a shade shorter than the original, this explains why fuel is still leaking out after a diaphram "pull" due to normal vaccum. As a result I put the original diaphram back in (it was in good shape) and no more leak. What is such a drag is that the bike was running so damn good after the carb rebuild and tune, I did this petcock thing just because it is 29 yrs old. Now the bike is running real bad, I can't even get it to idle. I think now that probably everything got wet, maybe even a little bit in the case. So the next thing is to dump the oil, clean the plugs and start over.....wonderful!

On a lighter note without the support on this site, all I would have is a 500lb paper weight...Thanks again!
 
I rebuilt mine... so far so good. It leaked a first, and then after some excercising of the pulse line it seemed to seat itself. Well see...

Steve
 
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