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1980 Petcock ? ASAP

  • Thread starter Thread starter gsvol
  • Start date Start date
G

gsvol

Guest
It is sucking air at the hole where the slot is for the flathead. Put your thumb over it while bike is running and u can feel it sucking a little on your thumb

I take it this is not right?
 
How much air? It does act as an air bleed. Turn it 90 degrees and see if it stops - keep in mind, though, that's prime position and the fuel may still flow after you shut the bike down (if prime still works).
If your bike isn't suffering from fuel starvation, then it's probably fine.
 
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not much air

i can free turn it ether way it wont stop, i can turn and turn it

i put chewing gum over it to stop it
 
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The petcock should not draw vacuum like you suggest. Something is wrong - most likely the diaphragm is ruptured, which can allow fuel to leak back down the vacuum line and into the carbs that way. Not good. A new OEM petcock costs about $75 + shipping from places like Boulevard Suzuki.
 
Nessism said:
The petcock should not draw vacuum like you suggest. Something is wrong - most likely the diaphragm is ruptured, which can allow fuel to leak back down the vacuum line and into the carbs that way. Not good. A new OEM petcock costs about $75 + shipping from places like Boulevard Suzuki.
Click to expand...

what if i gut it plug off the vac line? and put in a on off in the fuel line like a briggs and straton fuel shut off?
 
If you take one apart, you'll see that it is an air bleed and will suck air through the center. Like you say, not much. Your bubble gum trick effectively put your petcock in prime.
 
The plastic bit in the '80 petcock's selector valve seems to shrink over time. This results in a vacuum leak that prevents the diaphragm from holding the main valve open. The prime setting won't work, and the carbs will starve for fuel at highway speeds.

You can't rebuild it. Get a replacement as suggested if you have other symptoms. I've never checked to see if mine leaks where you describe, and I can't go check it now.
 
If by gutting it you mean removing the spring under the diaphragm - sure. But if it's running fine, why would you?
 
Not sure what bike you have, but most lawn mower fuel line is only 1/4".
 
Nessism said:
I bought a similar petcock from Z1 and the prime setting doesn't work correctly. Maybe just bad luck but have an OEM petcock on order now.
Click to expand...

How did it behave? My replacement (either from Z1 or PartShark, I don't remember) needed a pulse of vacuum to open it. So, set it to prime, turn her over a few times and wait a couple minutes.
 
Dogma said:
How did it behave? My replacement (either from Z1 or PartShark, I don't remember) needed a pulse of vacuum to open it. So, set it to prime, turn her over a few times and wait a couple minutes.
Click to expand...

My bike won't start without extensive cranking after being parked for a couple of weeks. No fuel in the float bowls. I'm familiar with the need for a vacuum pulse to activate the Prime system, but that doesn't work. Apparently the check valve doesn't hold, or it's leaking vacuum out the front like the petcock described in this thread. Haven't taken it apart to check yet.
 
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i just want to know if its OK to ride till i get a new one...IT RUNS FINE!!! just sucking a little air at petcock like i stated above
 
gsvol said:
i just want to know if its OK to ride till i get a new one...IT RUNS FINE!!! just sucking a little air at petcock like i stated above
Click to expand...

It should be okay to ride like it is. As a sanity check you might want to verify whether or not the fuel flow stops when the vacuum source is removed. If not, there will be fuel pressure on the float needles all the time (even when parked), and leakage will result in carb overflow and (likely) fuel getting into the crankcase and diluting the oil. Also, I'd verify there is no fuel entering the vacuum line and back-flowing into the carbs that way. A clear vacuum line will tell the tail here.
 
Nessism said:
It should be okay to ride like it is. As a sanity check you might want to verify whether or not the fuel flow stops when the vacuum source is removed. If not, there will be fuel pressure on the float needles all the time (even when parked), and leakage will result in carb overflow and (likely) fuel getting into the crankcase and diluting the oil. Also, I'd verify there is no fuel entering the vacuum line and back-flowing into the carbs that way. A clear vacuum line will tell the tail here.
Click to expand...


should i keep the vacuum leak blocked off or let it leak?
 
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