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1977 Suzuki GS750
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Discussion Starter · #1 ·
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 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.
 

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1977 Suzuki GS750
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Discussion Starter · #8 ·
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.
I would definitely suck if I can’t turn it off but I’ll give it a shot
 

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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.
 

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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.
 

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There is no “off” position.
 

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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
 

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1977 Suzuki GS750
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Discussion Starter · #14 ·
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 have yet to try it because I didn’t have the time yesterday
 

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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
 

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1977 Suzuki GS750
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Discussion Starter · #17 ·
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
So I tried putting a piece of inner tube in instead of the diaphragm and that didn’t work

I then put it back together but put the spring in front of the diaphragm hoping it would stay open butthe on position didn’t work, only the prime

I’ll have to find a way to block off the prime setting

any other ideas?
 

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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
 

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Quite honestly, I run my GS550 in the Prime position most of the time. I find that the vacuum “on” position doesn’t supply enough fuel for a spirited run through Deals Gap at high RPMs. (Even with a brand new petcock).
I switch it to “on” when riding to and from the play ground and when it’s parked.
 

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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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