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New petcock diaphram waste of time

  • Thread starter Thread starter rthor
  • Start date Start date
Don,
My dumb...
I thought the spacer you were talking about was the middle metal spacer on the diaphram itself. Now I see what you are talking about...you are referring to the plastic spacer that is placed between the diphram rubbers. I'll take a few mm off that and give it a try (on the week-end).
I'll let you know how it worked out.
Thanks for the tech support.
 
Baatfam said:
Ah, the good old days...

Remember to turn on the gas
Remember to turn on the lights
Remember to put up the kickstand
No gas gauge
No neutral light
No gear indicators
Use your arm to signal

My-o-my, how did we manage to ride at all....:p
Click to expand...

Minus the hand signals that sounds just like my wife's rebel, she has to turn the gas on / off, no rpms, no gear indicator, and well most the time the speed doesnt read... I should fix that cable.
 
I just bought a rebuild kit from Z-1 and rebuilt my pepcock this last weekend. Works fine now. No problems and the bike runs smoother now:clap:. Just followed the rebuild instructions found on this site.

Bob
 
As said by earlier posters your new diaphram will not seal properly if the small o-ring does not seal properly or that seating part of the petcock is worn. Also look at slightly stretching the spring for the diaphram as it may have lost some of its tension over the years.
Sometimes a slightly thicker o-ring from an engineering supplier can also solve the problem.

Just a last comment the holes in the one corner of the diaphram must line up with the spacer and the membrane and the body of the petcock - but you probably know that.
 
Ok, things to go over on the second attempt...

-check for blemishes/imperfections in the valve body
-polish the surface of the valve body with a tapered mandrel
-take a couple of mm off the plastic spacer
-stretch spring slightly
-try slightly larger o-ring

Thanks for all the suggestions guys. I wouldn't have likely considered any of these things. Your experience on this subject is most appreciated. I'll post the results sometime this weekend.
 
All dirt bikes (that I know of) use a manual setup like the Pingle. I admit quite a few street riders are not used to them, but they work very well but only if you remember to turn them off.

If you can remeber to take the key out of the ignition (somthing that isn't required on dirt bikes, you can surely to reach down and turn off the gas.

Just a thought.
 
I just rebuilt mine the other day and it works great. It seems like it is a hit or miss kind of thing reading this thread. Guess I got lucky. Good luck in whatever you decide/ pingel or rebuild.
 
One thing to keep in mind is that there are three different types of OE petcock. Pre 1980 with the large lever, the no lever 1980 petcock, and the 1981 and onward small lever petcock. The 1980 and later style use an O-ring on the diaphragm nipple to seal off fuel flow. The O-ring can dry out or the inside of the petcock body can corrode which will upset the seal. I've also seen some later type petcocks where the tapered plastic barrel gets scored up and binds in the petcock body. My opinion is that rebuilding the petcock is reasonable as long as the basic parts are in good shape - replacing the O-ring and/or diaphragm should fix it up. Switching to an expensive Pringle seems silly to me and completely unnecessary.
 
One of the first things on my "to do" list when reviving an old bike is the petcock, whether it seems to be working ok or not. I've rebuilt petcocks and I've replaced them. Obviously, replacing with a new one works every time. I've had mixed results with rebuilding, it's worked wonderfully twice, was a disaster once.

The one time it didn't work was on a Yamaha XS 1100. This bike has two petcocks, and they are only available from Yamaha dealers for about $90 each :!: Faced with this, and one petcock seemed fine, I tried a rebuild kit for the one that leaked.

The kit was the same brand as the others I'd used before (one Kawasaki, one Yamaha). This particular one seemed to fit ok, but after I installed and tested it, it leaked. Upon disassembly and inspection, I discovered that the rubber parts were swollen and deformed, evidently from reacting to the gasoline. I tossed the pieces, bit the bullet, and bought a new petcock from Yamaha.

I think that this is relevant to the aftermarket gasket thread going on right now on this forum. Evidently (at least on the XS 1100 kit), the supplier changed rubber formulas, and it wasn't chemically compatible with gasoline (kind of important on a fuel petcock!), whereas the earlier ones I had purchased were.

I guess the moral of the story with rebuild kits is you spends your money, you takes your chances.
 
rthor said:
I'm sure I'm not the only one to have experienced this problem, but try as I might, that new petcock diaphram was not going to seal. With the new part in place and all tightened down, gas would keep trickling out the spigott. I eventually gave up on it and put the old one back.
Has anyone out there had success with replacing the diapram? Is there something I have to do to make it work, or should I just accept the fact that I need to buy a new OEM petcock complete?
Click to expand...


you need to polish the metal due to porosity red 3M or green 3M works great.
rough surfaces won't seal to new rubber unless you smooth them over.
 
I gave it another try with the the new diaphram and it still will not seal. I tried all of the suggestions except for shaving a few mm off the plastic spacer between the diaphrams (I didn't want to modify that piece in the event that it wouldn't work and then I'd be SOL in getting the old diaphram to seal too).
There is definately a size difference between the OEM and the aftermarket diaphrams. The OEM one is slightly longer and will effectively seal off the fuel flow in the petcock valve body with the pressure from the spring. The new one is just a bit too short and just does not have the necessary travel for the oring to make contact with the metal seal in the petcock body. I don't think there is much I can do about that other than reduce the size of the plastic spacer by the difference. If I can scrounge up another plastic spacer, I'll try that as a last resort, (and if that doesn't work, I'm buying the new petcock...)
 
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