GS750L 1980 Petcock

[thkbaron]

So is it just me, or does the stock petcock for a 1980 GS750L appear to not have a shutoff/pri/on lever? THe one on my bike now has one but it's not a stock petcock.

 

[Steve]

Nope, that's the "dreaded '80 petcock".

I am not sure if I remember correctly which way is what, but I think with the slot verticle, it is in PRIME mode, horizontal is RUN mode. There is no RESERVE.

Unique thing about PRIME on those petcocks: it takes a brief application of vacuum to get it flowing, after which it will run continuously. If you need to use PRIME, set the petcock to the appropriate position, bump the starter to give it that one (or two) pulse of vacuum, then turn the key off for a bit and let it fill the bowls.

Fortunately, both of the '80 bikes in our stable are shafties, which were not "blessed" with those cursed things. :dancing:

.

 

[thkbaron]

Do you need to get that lever seperate then or is there a way to adjust the settings without a lever? I wanna replace mine, because I think I have a small issue with it. Seems to leak a tiny bit of fuel down the vacuum line.

 

[tom203]

Do you need to get that lever seperate then or is there a way to adjust the settings without a lever? I wanna replace mine, because I think I have a small issue with it. Seems to leak a tiny bit of fuel down the vacuum line.

Fix it or "tiny" might grow. Since you don't have the stock petcock , remove and find out what you got- someone might have modified the holes for a certain petcock or somesuch. You're likely to find a direct replacement and with a lever!

 

[cp___32]

My 550L has the same petcock as yours. When I got the bike I thought the same thing, that the lever had broken, but alas, it's the brilliant design for our bikes. If you still have the little tool tray under the seat I suggest adding a tiny blade screw driver to your kit. My dad had one he used to carry in his shirt pocket so that's what I'll be using. Also handy for adjusting those set screws in the carbs, so not a bad little tool to have around.

 

[Guest]

One way to fix it, is gut the petcock by taking out the vacuum parts, block off both vacuum tubes and place an inline shut off valve on to the fuel line.

 

[Nessism]

None of the various GS petcocks have an "off" position, such that fuel flow is mechanically stopped under all conditions. A simple fuel shut off valve could be added in line on the fuel feed line, only packaging the valve into the tight confines on some GS bikes could prove problematic.

The weakness of the lever-less petcocks compared to the various other GS petcocks is 1) they have no Reserve position, 2) a screwdriver is needed to switch between Prime and Run, 3) the Prime function requires a pulse of vacuum to open the diaphragm and allow fuel to flow, and 4) the check valve, which holds the diaphragm open after the Prime vacuum pulse opens the valve, is prone to failure and non-serviceable. Good thing about the leverless petcocks is they are cheap - about $45 shipped. Get two and keep one as a spare "just in case".

 

[DanTheMan]

My original 3.2 gal tank (which I still have) has the screwdriver petcock, and it was working fine until I upgraded the tank on my '80 850L to a 4 gal tank which uses the petcock I had on my 80 850G parts bike. I couldn't guarantee how well it works now though since it's been dry for a couple of years now sitting in my garage.
And, Steve is right on the valve positions, vertical slot=PRIme, horizontal =Run.
As far as replacements go, the bolt hole spacing is different than the petcocks with handles on them, it's narrower, but I don't remember the measurements.

 

[tom203]

One way to fix it, is gut the petcock by taking out the vacuum parts, block off both vacuum tubes and place an inline shut off valve on to the fuel line.

Too much work, just get new one for $50 (with lever) and worry about other stuff.

 

[Nessism]

Too much work, just get new one for $50 (with lever) and worry about other stuff.

Check petcock clearance to the carbs before ordering non-standard petcock. The lever-less petcock is low profile, one of the reasons Suzuki adopted it.

 

[Guest]

Hi, petcock in my 1980 GS850L has never gave me any trouble, it was horizontal when i got her many years ago and i just let it stay there,now i know how it works, thanks to you guys.*But* she hasnt been going right for a while now and iv done the carbs, and has a good healty spark, im no expert, is it possible its a bad Gas tank Seal not allowing any vacuum to be created in the tank ?






alshio reg.1982 GS1100L.

 

[tom203]

Old petcock = failure prone; just get new and have no doubts.
Maybe this one would work on your 1980.....


http://www.georgefixs.com/servlet/the-524/1980-GS550,-GS750,-GS850,/Detail

 

[Guest]

There is no vacuum in the tank, it is gravity flow and the vacuum from the engine through the #2 carb vacuum port, is what creates the flow. If you don't have a tight fit with the hose or the carb boot you can loose vacuum causing the petcock to shut off. I just learned this when I was inspecting my intake manifold boots, the #2 boot was hard and wasn't sealing good. I would be tooling along and the engine would just die, fuel starved.

The problem with this type of petcock is its low profile (very tight fit between the petcock and the top of the air box). I've yet to find a manual replacement because of the tight fit. Besides the bolt holes are 50mm apart. Manuals I've found are only 40-44 mms. Rebuilding this type of petcock tends to be fruitless as I have a few kits I've tried. Think I have acquired 4-5 of these petcocks over the years.

Hi, petcock in my 1980 GS850L has never gave me any trouble, it was horizontal when i got her many years ago and i just let it stay there,now i know how it works, thanks to you guys.*But* she hasnt been going right for a while now and iv done the carbs, and has a good healty spark, im no expert, is it possible its a bad Gas tank Seal not allowing any vacuum to be created in the tank ?






alshio reg.1982 GS1100L.

 

[RobG1970]

Guys, I like Mr. Bill search and search for a manual petcock with 50mm bolts with NO luck, I even went so far as to have Suzuki research to see is one was made to replace the CRAPPY vacuum type that we have. What I and some others came up which is, just by a NEW Good quaintly replacement from Suzuki or K&L, do NOT buy NOS (new old stock) you will have the same old issue of the diaphragm inside dry rotting and then the pin hole leek with cause the gas to go back down the vacuum line into the #2 carb, fill the cylinder, then into your block, and well finally cook your bearings. What I am going to also do for overkill is put a manually petcock in line with the fuel line from the tank, and a small one in line with the vacuum line… yes.. I know this is a bit much, but at least I can shut BOTH Lines off when I am not riding for any long period of time.​

There is no vacuum in the tank, it is gravity flow and the vacuum from the engine through the #2 carb vacuum port, is what creates the flow. If you don't have a tight fit with the hose or the carb boot you can loose vacuum causing the petcock to shut off. I just learned this when I was inspecting my intake manifold boots, the #2 boot was hard and wasn't sealing good. I would be tooling along and the engine would just die, fuel starved.

The problem with this type of petcock is its low profile (very tight fit between the petcock and the top of the air box). I've yet to find a manual replacement because of the tight fit. Besides the bolt holes are 50mm apart. Manuals I've found are only 40-44 mms. Rebuilding this type of petcock tends to be fruitless as I have a few kits I've tried. Think I have acquired 4-5 of these petcocks over the years.