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Answer to high idle when warm and question regarding petcock

  • Thread starter Thread starter jeffgs
  • Start date Start date
J

jeffgs

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I asked this question a week ago regarding my climbing idle as the bike warms. The diaphram in my petcock let go and was pumping fuel into the vacuum supply of my carb. Now my question is straight forward, can i replace it with a normal on, off non vacuum petcock? If so is there a certain size I need? I cannot see the upside to this vacuum opperated petcock. Especially now that i have a constant fuel drip because i cannot shut it off.

BTW, restoration has started, will post progress. Carbs will need to be done and rear brake shoes but nothing else needed mechanical wise.
 
The vacuum operated petcock is actually pretty stinkin' cool. I don't ever have to worry about whether or not I've turned my gas off after parking the bike.

I did rebuild mine with a kit from Amazon or Ebay, this was three years, ~8000mi. ago and it still seems to be operating quite well!
 
It would be nice if you could go to User CP and put the year and model of your bike in your signature line so we know what we are dealing with. Rising idle is usually caused by a vacuum leak that opens up when the bike gets to operating temperature. The usual suspects with bikes this age are leaking intake boots or intake boot O-rings. Robert Barr sells O-ring kits necessary for rebuilding these carburetors and boot O-rings at a very reasonable price (http://www.cycleorings.com). The petcock can be replaced with a stock valve, or Z1 Enterprises carries aftermarket valves that are vacuum or manual. The vacuum valve is an added safety feature because manual valves left on can end up filling the crankcase with gas if the needle valves don't hold. Z1 is also a good source for gaskets. You might want to consider a stainless steel braided brake line for the front brakes in your rebuild. The rubber lines expand especially the old lines. The stainless lines hold the expansion to a very low rate, giving you better brake power then stock lines. Welcome to the forum.
 
Depending on which model GS you have, you can turn it into a manual petcock if you wish.
 
My bike is a 1981 GS450. I was trying to load that into my profile as soon as I can figure it out.
My plugs have a strong smell of gas and are dark and wet around the perimeter. When the bike is warm it revs up, if i turn the petcock to prime and disconnect the vacuum the idle goes back down and the bike goes down the road running better until it runs dry. i have found fuel leaking out the air horn on the driver's side carb. That line has a strong fuel smell and i have sprayed all intake boots with carb spray with no rise in rpm.
 
Btw
Regarding suggestions, I take them. I have been off street bike for 10 years and am eager to learn. Not interested in being arrogant and am no hotshot. Looking to be safe and show my wife appreciation for going behind my back and bringing this bike home for me by cleaning it up and making it a nice bike again.
 
in all honesty i would just buy a new OEM vacuum petcock. less hassle and you know its good more to the fact its the right part for the right job.
 
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