Manual petcock?

This may not belong in carburetor, but it's the only fuel related subforum I see. If it shouldn't be here, please move it.

Can anyone tell me where to find a non-vacuum operated petcock for my CSR 750M1? I've searched the forums and seen references to Brown Family Racing, but they seem to have gone the way of the dodo

Went out for my first ride since getting it home and after about a mile it died. Little troubleshooting. Definitely getting spark. Air filter was clean and clear. Really seemed like it wasn't getting fuel, but the tank was half full. Switched the petcock to manual override. Fired right up and ran fine. I know it could have a vacuum leak keeping it from pulling open, but either way I don't like the idea of a vacuum petcock.

Thanks!

Golan and Pingel both make manual petcocks, but you may need to use an adapter to fit one to your fuel tank. Check out www.z1enterprises.com . They have adapters and petcocks. Ed

I've had good luck on ebay finding manual petcocks to replace vacccum ones. You do need to know the bolt spacing .

There are numerous OEM Yamaha manual fuel cocks that are very reasonably priced, if not cheap.
$25 or so is cheap for a made in Japan fuel valve. I think most of them have a 34mm bolt hole spacing.
search EB for Yamaha fuel cock or Yamaha Raptor fuel cock. or fuel valve.

Have you tested your petcock to see if that is truly the problem? Vacuum petcocks will work reliably as long as they are in good repair.
The easiest/cheapest solution would be to rebuild your stock petcock. I find Kawasaki (and Honda) vacuum petcocks to work pretty well. Yamaha not so much.
Here is a good tutorial for rebuilding petcocks: Petcock Rebuild

Thanks for the feedback everybody. It definitely has a problem. Went out to look at something else and smelled fuel. Bottom of one of the carbs is wet so I unhooked the tank, pulled it, and put a pan under it. If there's any gas in the pan tomorrow looks like I'll be pulling the plugs and draining the oil just to be sure the engine is safe.

I know that manual petcocks can leak too, but that vacuum diaphragm is much thinner than the other seals. Plus I like a petcock with an actual off position. I learned to ride before vacuum petcocks were a thing, so it's not as though I'm going to forget.

Thanks for the heads-up on the potential Yamaha Raptor crossover. I'll check it out and see if one fits mine.

Before you spend any money check that the fuel tank is breathing. The breather is in the gas cap. A clogged breather will cause fuel starvation.
If you left the petcock on "prime" while the bike was parked, it could be the reason one of the carbs was wet. If the petcock was definitely in the off position then I would think it needs repair.

I like my vacuum petcock, having a auto shut off is a good thing.
If you are getting gas leaking out of the carbs it is because the floats are set wrong and or the float valve needle and seat are dirty or worn, probably just dirty.
to clean a float valve seat I chuck a cotton Q-tip in a drill and use a little metal cleaner to polish up the seat and inspect the float valve needle for wear after cleaning.

The only thing that screws up in my 78 vacuum petcock with over 85,000 miles on it is the rubber seal for the selector switch, I have to replace that every 2 years because of the modern ethanol enhanced gas we are stuck with :pinch:

If your bike dosn't get gas when the selector switch is on run then your petcock is probably working as it should and you need to find the vacuum leak.
Try a smaller hose, if it is a tight fit you don't even need clamps.

Well it is leaking, not through the vacuum port though, so that's a good thing. On "run" I'm getting about one drip out the fuel port every 1.5-2 seconds. So not super fast, but fast enough

The cap is breathing and I didn't leave it on "prime." I'd have been surprised if I had. I'm ADHD, so if I don't create routines that I always follow I overlook everything. I've only ever had one other bike with an automatic petcock. Just as when I'm getting out of my car I look at the keys in my hand then lock the door, getting off the bike I look that they keys are in my hand then reach down and put the fuel valve where I want it.

I was a mechanic for a couple of decades. Autos and heavy trucks, but still, machines. It's fine that some people like their automatic fuel taps. I'm glad that option exists for those who want it. But having worked on machines for so long, my perspective is that the more complicated you make a thing, the more potential failure points you have. Same with my car. It's the most basic Civic made that year. The only power accessory is the windows and if I could have found one with crank windows I"d have bought it.

Might be that there's a vacuum leak somewhere, and I'll check that, could also be that something in there is gunked up and keeping it from moving properly. After all, in 36 years it's only been ridden 5700 miles. Plenty of chance to sit around with gas in places it shouldn't be stored. I'll either replace it or rebuild it. Since either way I've got to pull it off, I think I'll take it apart and see if there's a passable way to modify it so that it functions as a manual. I'll check the vacuum operation of the valve too, since I have to drain it to pull the tap off.

Well there was a vacuum leak, at the petcock. Not huge, but big enough that it would have let the valve close while idling. So now I decide between rebuild, replace with non-vacuum, or modify for non-vacuum. Probably the second one. The other two will require getting seals since, yeah, that selector seal is looking pretty dodgy. If I get a Raptor petcock, I get rid of the vacuum action, and I get seals made with modern fuel in mind. That's a win-win in my book.

With a vacuum petcock, you can use it as a manual petcock, but you won't have a reserve.
Remove the vacuum line & cap the ports with good automotive vacuum caps: ON & RES now function as OFF; while PRI functions as ON.
I would replace the diaphragm o-ring. It can get hard & deformed. buff & inspect the mating surfaces to ensure a good seal.

Have you measured the bolt-hole spacing yet? Please post the measurement when you get a chance. Thanks.
As I noted above, the 1981 KZ650-CSR is 34 mm. The KZ750-CSR is almost completely different, so it could be 44 mm.

Fumbled to find the Reserve setting on my Pingle a couple days ago while sputtering up a long hill. Just kept switching back and forth from ON to OFF, without realizing that RESERVE is half-way between. After the momentum stopped, I thanked God no one was watching.

Won't go through that again if I can help it, but learned the hard way...as usual. :blush: