Petcock Replacement for a '76 KZ750

mind2find wrote:

A quick check on testing my float level. Can I run water through these guys so I don't have to put them back on the bike to test if I got the float level right?

Don't think that will work, my friend.

Water and gasoline have different densities. So if you adjust the level with water, your float level will be different with gas.

Also, I had a problem with my floats sticking, and I found the problem was that the float "biscuits" were slightly angled outward so that they were catching on the side of the bowl. I bent them back in, did my adjustment, and no more sticking.

Just to finish up this thread (I'll start another one related to my overflow issues) the petcock is fixed!!!


If you remove the metal "selector" knob by simply removing the screw above it, the knob and a spring come out. Beneath that is a small plastic piece that actually channels the gas from the tank to the two ports.


It is possible for this to be turned 180 degrees so that the knob & spring can still fit back into their slot on this plastic piece, but this rotates the two holes that are supposed to line up with the "on" and "reserve" positions, functionally breaking it.


Moving this into it's correct place and putting some gentle pressure to make sure this plastic piece was in place took care of my malfunctioning.


Apparently a previous rebuild screwed this up. I shoulda checked when I did mine but didn't even know the plastic piece could be knocked out. :pinch:

Fuel should not drizzle from overflow nipples even if petcock left open.

Fuel enters the float bowl through the float needle seat. The float needle serves as the seat doorway. When fuel reaches proper level in the bowl, the float rises and presses the pointed float needle tip into the seat (closing the door) which supposedly blocks any more fuel from entering the bowl.

A poor seal between the float needle seat and pointed tip of the float needle is like a crack in the doorway which continues letting fuel into the float bowl, which then overflows.

Some float needles have a rubber point while others have solid metal tips.

The closure fit between float needle seat and float needle tip must be perfect to completely seal. That's one reason it's best to replace them in pairs, and not to mix and match during reassembly.

A grain of grit in the doorway can result in a steady stream of fuel from the overflows.

Some crud might be displaced by using Seafoam or similar product mixed into the fuel.

Turning off a properly operating petcock stops fuel from reaching the doorway, but does not repair the crack.

If float level is adjusted properly, and floats are floating, and fuel drizzles from float bowl overflows, it's a safe bet that the float needles are not properly seating inside the float needle seats.

Thanks Patton,

You are definitely right. Fixing the petcock isn't a fix for my float issue. I'm working that out right now. Please see this (new) post .