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Suzuki gs750 petcock

1401 Views 32 Replies 5 Participants Last post by  Bobby05
Does anyone know if someone makes a non- vacuum petcock for a 1977 Suzuki gs750

I got new carbs and they don’t have vacuum ports on them. I now need to find a petcock that doesn’t have a vacuum diaphragm in it
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There's a bush fix if you just want to defeat the vacuum part; you can replace the spring loaded diaphragm part with a chunk of rubber cut out of an old inner tube.
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Yes to that and it also blocks fuel from leaking out the vacuum ports.
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There's actually 4 parts you won't need any more, the o-ring, diaphragm, spring and the spacer plate with the round hole will all become unneeded. Should be relatively obvious once you have it apart.
Pretty sure the off position will still work, but you might want to check that. would suck if you can't turn it off.
If you turn it to off position and can't blow through it anywhere, you're good to go.

I like bush fixes, less time in the shop or waiting for parts and more time riding.
It's tricky to drill nice clean holes through rubber for the screws to go through, tools that you use for leather or wood work best. Hole punch for leather would be perfect.
There is no “off” position.
that would present a problem, unless you plug one of the ports.
:sneaky: although if there is no vacuum and the spring is strong enough and the diaphragm is still working that would be an off position. omg it just got complicated I hope he fixed it already
I think you are going to have to find a way to plug the prime position opening so you have an off valve. The reserve fuel pipe probably still flows through what was the original vacuum controlled port opening.
(y) confidence is high
bummer, I don't like the idea of leaving the diaphragm as point of failure, if you can't see a way to modify it to do everything it needs to do, replacement might be the only option. Plugging the prime circuit sounds easy enough but keeping the reserve and lower drain both working might be a challenge, do you have a local scrap yard? I'd be taking the tank and finding something that has an off.

:cool: did you get nice carbs
Pingel is still a good recommendation if you don't mind the cost and order process
Thirsty bike.
Montesa 360VA needed 2 fuel taps usually set on reserve feeding the single Bing carburetor or I could starve it for fuel. 2 gallons of pre-mix race fuel went about 30 minutes, but wow did it ever fly :cool:

They had a very cool ball bearing in rubber petcock that worked great, but wore out after a few years
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Interesting, my bike bogs down in high rpm’s
I thought you said it runs like a champ now :unsure: Pods will do that to you, the fuel starvation issue 8Ball described is not something you would experience on the street unless you are trying to outrun a road rage situation.
Post up a picture of all the spark plugs right after a good hot run and you might get some helpful input on the rich/lean thing. One fuel line per carb would solve any fuel pressure concerns. Ignition timing needs to be spot on
& I think you are going to end up needing to stack the carbs to make them tune perfect.

What's the fuel consumption over distance like too? Fuel efficiency is a good indication of an engines total health.
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