It's Time for my Annual Petcock Diaphragm Change

pingels are a bunch of extra money but worth it i try to get one for all my customers that end up with fuel system problems i personally have 4 that i have had for at least 10-15 years and never had a failure yet. to me the extra expense is worth it no more fuel leaks in my shop no more wrecked paint on my cases. it's a win/ win situation for me.

Just another thought...

The one time I did have a leak at the petcock, it looked as if it was leaking at the diaphragm out of the sides, but as it turned out, it was seeping at the mating surface with the tank and wicking down the petcock. I just cleaned the mating surface and tightened the mounting screws.

Is there any chance it's leaking higher up than the diaphragm area?

Patton - The design of my particular petcock allows fuel to flood one side of one of the diaphragms. It is supposed to seal via some small raised areas on the housing and on the plastic center piece. It is no wonder it leaks.
Motor Head - Yes mine looks like what you have shown.
JMKZHI - I don't know the brand, but it came from Z1E. I believe you have a great idea about the 2005 police bike and a new OEM part being the answer. COME SEE MY NEW OLD TOY. (Hint - See the signature).
larry cavan - The petcock completely stops the flow of fuel when the engine is off, but will start leaking again when engine is running or petcock is turned to "Prime".
loudhvx - No not leaking from above. That would be too easy.
All:
Tell me about a non-vacuum petcock. Do you have to shut it off manually every time you stop? I like the safety factor of the vacuum unit - when it works.

WABBMW wrote:

Tell me about a non-vacuum petcock. Do you have to shut it off manually every time you stop? I like the safety factor of the vacuum unit - when it works.

Well, you 'should' turn it off after every ride. You can search Ebay using your measurement. Put one of these stickers on your gas tank until you get used to it.

I've had a vac petcock for some time, and it leaked in the ON/RES position while running, but not the prime position.

I pulled the vac line and plugged the carb, turning the petcock into an on/off, not worrying about the vac at all.
Turn to prime for on, and either on or res for off.

My other ON/OFF petcock leaked and i just sealed it with permatex motoseal, and it hasn't leaked for 3 years.
Just have to dab a very thin film of the stuff on both surfaces with a finger, then assemble and let dry overnight.

The on/off pertcocks don't require being turned off, but it is a good suggestion if your going to let the bike sit a while as the old float valves can leak slowly causing overflow.

Good Luck!

yes it has to be shut off but after awhile you don't even think of it, it just becomes automatic. as far as safety goes nothings better then turning it off yourself.

One neat thing about the manual petcock is ability to turn fuel flow off a short distance before reaching home and allowing the engine to idle until the float bowls empty just before pulling into the garage.

I like the idea of parking with float bowls empty, just in case it's a few days before again running the engine.

On the diagram Motor Head posted, where is the second diaphragm and plastic piece mentioned?

Good Fortune!

Patton wrote:

One neat thing about the manual petcock is ability to turn fuel flow off a short distance before reaching home and allowing the engine to idle until the float bowls empty just before pulling into the garage.

I like the idea of parking with float bowls empty, just in case it's a few days before again running the engine.

On the diagram Motorhead posted, where is the second diaphragm and plastic piece mentioned?

Good Fortune!

I second that! I always shut the fuel off when I turn onto my road. The carbs are almost dry by the time I pull into the barn. This helps keep the jets from varnishing up if the bikes sits for a few weeks.

Patton wrote:

One neat thing about the manual petcock is ability to turn fuel flow off a short distance before reaching home and allowing the engine to idle until the float bowls empty just before pulling into the garage.

I like the idea of parking with float bowls empty, just in case it's a few days before again running the engine.

On the diagram Motor Head posted, where is the second diaphragm and plastic piece mentioned?

Good Fortune!

The plastic plate piece is not shown separately in the parts diagram, but it is there. I just bought a new diaphram kit from Z1E and installed it and it leaked immediately! DOA! Before you ask : the parts are not worn, warped, or faulty in any way. These diaphrams are crap! I'm calling Z1 tomorrow and see if they will warranty it. The tap leaks out of the vent hole on the side of the diaphram housing. And fuel does contact the diaphram when in ON or RES.

cyclhed wrote:

Patton wrote:

One neat thing about the manual petcock is ability to turn fuel flow off a short distance before reaching home and allowing the engine to idle until the float bowls empty just before pulling into the garage.

I like the idea of parking with float bowls empty, just in case it's a few days before again running the engine.

On the diagram Motor Head posted, where is the second diaphragm and plastic piece mentioned?

Good Fortune!

The plastic plate piece is not shown separately in the parts diagram, but it is there. I just bought a new diaphram kit from Z1E and installed it and it leaked immediately! DOA! Before you ask : the parts are not worn, warped, or faulty in any way. These diaphrams are crap! I'm calling Z1 tomorrow and see if they will warranty it. The tap leaks out of the vent hole on the side of the diaphram housing. And fuel does contact the diaphram when in ON or RES.

You can just ditch the whole petcock crap and tap a hose fitting into the bottom of the tank. Then use a simple in-line shutoff valve for snow-blowers (designed for tough elements), and it will not leak for many years!

Best of luck - i hate petcocks.

TeK9iNe wrote:

cyclhed wrote:

Patton wrote:

One neat thing about the manual petcock is ability to turn fuel flow off a short distance before reaching home and allowing the engine to idle until the float bowls empty just before pulling into the garage.

I like the idea of parking with float bowls empty, just in case it's a few days before again running the engine.

On the diagram Motor Head posted, where is the second diaphragm and plastic piece mentioned?

Good Fortune!

The plastic plate piece is not shown separately in the parts diagram, but it is there. I just bought a new diaphram kit from Z1E and installed it and it leaked immediately! DOA! Before you ask : the parts are not worn, warped, or faulty in any way. These diaphrams are crap! I'm calling Z1 tomorrow and see if they will warranty it. The tap leaks out of the vent hole on the side of the diaphram housing. And fuel does contact the diaphram when in ON or RES.

You can just ditch the whole petcock crap and tap a hose fitting into the bottom of the tank. Then use a simple in-line shutoff valve for snow-blowers (designed for tough elements), and it will not leak for many years!

Best of luck - i hate petcocks.

I know what you mean! I ditched the vacuum cock and bought a pingel adaptor and used a 3/8npt on/off/res valve I had from a previous project. Works great!

Here's the picture again, I added it to another post also. Just so everybody can see how easy it works. I don't trust a fuel valve that you can't shut off!

Motor Head wrote: I'll give my experience. 82 KZ1000, pretty sure the diaphragm was original, took a 3600mi trip. Added Sea Foam to tank 250mi from end of trip, diaphragm started leaking in 40mi or so. So coincidence, or just do to fail? I think from looking at it that is was from the additive. Which by the way didn't help, I found a small piece of air filter foam in a air bleed. Should have removed and washed that housing. Hind site = 20/20 every time.
But it will be quite awhile before I can say if the replacement, from Z1, will hold up.
So do you run an additive in the fuel?

So just do an update on the Vacuum Petcock Diaphragm that I replaced last summer.
Still working perfectly, nearly 4500mi since install. I was doing some checking with my stethoscope, and the Vent on the diaphragm plate was pulsing out air. I could also Feel the diaphragm moving. The vacuum hose was still hooked up as original, to the 1 #2 carb. With the pulse in the intake tract you get a movement of the diaphragm with each piston cycle. So I used a Tee to add it to the #1 carb which flattened these pulses, of course, and the venting/ movement noise is gone. Double checking with Mighty Vac confirms the pulse with the hose on one carb, and steady vacuum with a Tee to two carbs.
I'm thinking that the constant movement, at least at Idle would add to a premature failure, especially with the replacement diaphragm as it is lots thinner.