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Petcock or Carb synch....Place your bets!!

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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1981 gs 450, left side plug is fouling out, took apart carbs and cleaned, same thing happened, unhooked the vacuum line and ran on prime, fired right up, ran alright, seemed like it blew a bunch of crap out and then stopped smoking out of the exhaust, tried out the petcock and seemed like it was working, fuel flowed when in prime, not in reserve or on. Could the carbs be clean but not synched right. It will foul out a new plug pretty quick with city driving, stays good on highway until i have to stop then won't fire again. Doesn't seem to foul the plug when the vacuum line is unhooked. What do you all think?
 
There seems to be a rash of carb issues with these old bikes...Why have those vaccum petcocks? I think a regualr ol fuel vavle will solve lotsa problems from the get go..I think you may have answered your own question...With the vaccum line off ,,,it works! Maybe just get an on/off fuel valve...I think Pingle even makes one with reserve...Then go from there..Good Luck!
 
sorry, i don't think i said this before, When i unhooked the vacuum line and pluged the place in the carbs where is would connect, I only made it two blocks before the bike stalled and I had to reconnect it and set it to prime to get it to start again, I was running it in the on position when i had it plugged and it died. I really hope it is a petcock problem.
 
OK...so you have gas...possibly too much in your fouled cylinder...which would lead one to a carb problem with that cyclinder. Your plug is wet with fuel in that cyclinder? Are you sure its firing...Hows the plug in that cylinders partner? Check for bad wires or loose wires/coil ground. Float stuck open? Lotsa stuff to look at.
 
If you are fouling a plug and it is not oil then you may have 2 problems.

1. The fuel level is set to high in the bowl

2. The fuel float needle is leaking or trash is causing it not to close all the way
 
IF YOU PLUG the vacuum line you have to run the bike on prime it will not get any gas in the on position YOU have a leaking petcock diaphram
 
I vote petcock. I think that your petcock is leaking fuel through the vacuum line, causing a rich condition and carbon fouling in the left cylinder.

Try this: make sure the bike is cold so nothing catches fire. Put the petcock on RES. Then take the fuel and vacuum lines off the carbs. Suck on the vacuum line and be prepared for a mouthful of gas. This should not happen but I think it will. If the petcock is good there will be no gas in the vacuum line but if the diaphragm is broken gas will be sucked through it.

And checking the carb sync is also still a good idea.

Michael
 
I bet on petcock. I had the same problem with a fouled out #2 cylinder and the exhaust on the side that the fuel line hooked up to was REALLY rich. The sparkplug @ #2 was always sooty too. Turns out that fuel was coming in the fuel line from the petcock AND from the vacuum line too!!
I ditched the crap-ass vacuum-petcock and got a racing Pingle petcock that doesn't use a vacuum. Since then the problem has stopped.
But now I have other fuel mixture problems cause I'm always dinking with my bike hehe.

But thank pingle the main problem I was having is gone!!! It's all easy from here!

PINGLE PETCOCKS ROCK!!!!
;D
Dm of mD
 
yarddesigner said:
sorry, i don't think i said this before, When i unhooked the vacuum line and pluged the place in the carbs where is would connect, I only made it two blocks before the bike stalled and I had to reconnect it and set it to prime to get it to start again, I was running it in the on position when i had it plugged and it died. I really hope it is a petcock problem.
Click to expand...

That is how it SHOULD work

When you disconnect the vac line in 'ON', your bike will burn the gas that is in the carbs & fuel-line, but will not be able to feed any more gas.

When you turn the petcock to PRIME, this bypasses the vac-operated mechanisim, and allows unrestricted fuel flow.

That you went for 2 blocks & stalled indicates that your vac-operation is working fine...
 
So Wait, aren't you guys telling me different things, some of you are saying that it is the petcock and then the last message says that the petcock is working fine.
 
yarddesigner said:
So Wait, aren't you guys telling me different things, some of you are saying that it is the petcock and then the last message says that the petcock is working fine.
Click to expand...

It seems that your petcock shuts off OK, so that it flows in the correct positions. That's what Dave_A was saying.

I was saying that in addition, you have may fuel leaking down the vacuum lines. That's not right.

In all, your petcock very likely needs replacing. It is probably "partly" malfunctioning.

Is that any clearer? ](*,)

Michael
 
thanks, that answers that, I'm gonna get a new petcock and hopefully i can ride this summer without a pocketfull of spark plugs
 
Buy a pingle petcock.
Best investment you could make on this bike.
If you buy another stock petcock you will have to do this again...and again...and again like I did before my pingle petcock.

Dm of mD
 
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