Any non-vacuum petcocks for 91 - 03 750 Nighthawks?

[slmjim n Z1BEBE]

Looking for an old-style, non-vacuum-controlled, simple OFF/ON/RES petcock that's as close to PnP as possible for our '93 CB750 Nighthawks.

Anyone found or running one?

slmjim & Z1BEBE

[Gene]

 Did you check Ebay?

[Bob H]

I did think about it, decided against it. Figured I would rather rely on the vacuum operated valve - if it ever failed it would just be the same as forgetting to turn the petcock off. Then you are relying on the float bowl valves to prevent fuel overflow.

Why do you want one? The only reason I would have is that if my bike sits for 7 days or more it is slightly harder to start. I put a mity-vac to the petcock and discovered that if I let the fuel flow for a few seconds it starts quickly after sitting 7 days.

Since I recently changed out all vacuum tubing and fuel lines, they are nice and flexible. so I just pull off the vacuum line to petcock, grab a length of extra tubing and put it on the petcock and apply light vacuum for a moment. Then the bike starts immediately if it has been sitting. (I drain the carbs if it is going to sit more than a month)

[slmjim n Z1BEBE]

I've done the vacuum pump prime too. It's just enough hassle to make doing so well..., a hassle.

Might try a tube on the petcock's diaphragm breather nipple, to see if blowing into it, like blowing up a balloon, would actuate the flow diaphragm.

We've lived with Kawasaki Z1's for decades. They have manual petcocks. The result is, turning any petcock OFF is automatic, second nature.  Same for our Nighthawks; petcock is set to OFF when parking.

slmjim & Z1BEBE

[Bob H]

Might try a tube on the petcock's diaphragm breather nipple, to see if blowing into it, like blowing up a balloon, would actuate the flow diaphragm.

No, that would pressurize it.
I can prime mine by pulling the vaccum tube (stock it connects to #2 carb intake) and placing a length of spare vacuum line, and suck on the end of it.

VERY little vacuum is required. Fuel starts to flow with a mity-vac that has not yet reached any numbers, just the slightest pull on the lever.

We've lived with Kawasaki Z1's for decades. They have manual petcocks. The result is, turning any petcock OFF is automatic, second nature.  Same for our Nighthawks; petcock is set to OFF when parking.

OK, you would be a great candidate for a manual petcock.
Most of the parts on the 91-2003 NH 750 are common to other Honda's (front fender and the swingarm are also found on the Magna, etc.) I would think the petcock is a fairly standard thread, and it simply has an O-ring where it connects (that is what failed on mine, the O-ring got flattened out and started to drip)

[slmjim n Z1BEBE]

Might try a tube on the petcock's diaphragm breather nipple, to see if blowing into it, like blowing up a balloon, would actuate the flow diaphragm.

No, that would pressurize it.

Didn't make myself clear.

There's two ports (nipples) on the petcock's diaphragm cavity.

The rear port is the vacuum port, connected to the #1 intake that applies vacuum to the diaphragm, opening the diaphragm's needle valve to allow fuel flow. The other port (the breather port) is on the front side of the diaphragm cavity. That port is simply open to atmosphere. That allows a small volume of air to enter the diaphragm cavity on the opposite (breather) side of the diaphragm from that which has vacuum applied. This is so the diaphragm can move freely under vacuum, and allows for the air to exit the breather side when vacuum is removed from the vacuum port and the diaphragm relaxes.

Pressurizing the atmosphere side of the cavity moves the diaphragm in exactly the same way as vacuum does on the vacuum side. Like the vacuum side, only a small volume and amount of pressure is needed on the breather side to move the diaphragm.

Attaching a length of tubing to the breather port and blowing into it to apply continuous pressure will open the diaphragm's needle valve to start fuel flow. Imagine blowing into a very thick milkshake; that's enough pressure to achieve fuel flow.  A couple or three continuous 10 second pressurizations (blows) will prime the carbs if they've been drained. No vacuum pump needed. The vacuum hose from #1 doesn't need to be removed from the petcock when doing this method.

 If constant fuel flow is needed to, say, begin draining the tank, a vacuum pump is much more convenient.

Good Ridin'
slmjim & Z1BEBE

[Bob H]

Pressurizing the atmosphere side of the cavity moves the diaphragm in exactly the same way as vacuum does on the vacuum side. Like the vacuum side, only a small volume and amount of pressure is needed on the breather side to move the diaphragm.

Reminds me of the elderly couple that wanted to spice up their marriage.

"Suck Edith - Suck"
"Blow is just an expression"

[Pete in PA]

Never thought about this (sometimes miss the obvious). I could leave a section of hose installed there and use it to prime the carbs.