Petcock question

If the bikes been sitting for a long time the petcock needs rebuilding and running on prime is fine but when you run out of gas that's it no reserve when using the prime setting.
Mark

Pwallace30 wrote:

I was able to get my fuel lines worked out and take the bike up and down my street for its first ride in 20 years. I still have a petcock problem though, the bike runs fine when my petcock is turned to PRIME, but when I try and run it on FUEL, it will run for 5 mins or so then the bike will shut off. Could it be that I have a vacuum problem? Also what problems will I cause if I continue to run my bike on PRIME? Thanks

Vacuum petcock as shown in 77-79 KZ1000 FSM has three handle positions: RES, PRI and ON. There is no "FUEL" position, although the word "Fuel" might be inscribed on the handle as do earlier manual petcocks.

The handle inscription "Fuel" has no bearing on petcock position and should be ignored. Whichever position mark, RES or PRI or ON, is being covered by the petcock handle is the petcock setting.

The handle pointing up is RES (Reserve) position.
The handle pointing down is ON (the normal position).
The handle pointing sideways is PRI (Prime)position.

when my petcock is turned to PRIME, but when I try and run it on FUEL, it will run for 5 mins or so then the bike will shut off. Could it be that I have a vacuum problem? --- will interpret the word "FUEL" to mean the petcock position is ON (i.e., the handle is pointed down).

In the ON position, with proper vacuum applied, fuel flows until reaching the reserve level inside the tank.

In the RES position, with proper vacuum applied, fuel flows until the tank is empty.

In the PRI position, with or without vacuum applied, fuel flows until the tank is empty.

Am thinking the problem might be that tank fuel level is low (down to or below the reserve level), so the PRI petcock position is allowing fuel to pass through, which fills the carb floatbowls. Then, when turned to the ON position, the bike runs for awhile until exhausting the fuel inside the floatbowls. All normal.

However, if the fuel tank is full, and the bike won't keep running with the vacuum petcock set in the ON position (handle pointed down), then something is amiss inside the petcock or the petcock isn't receiving vacuum (for whatever reason, such as cracked, kinked or clogged vacuum tube, or leak where vacuum tube connects to carb nipple or petcock nipple).

Good Luck!

I'll first try filling the tank. But running it on Prime for a while wont hurt anything? Thanks

Pwallace30 wrote:

I'll first try filling the tank. But running it on Prime for a while wont hurt anything? Thanks

Nope --- but should heed Mark Wing's advice about risk of running completely out of gas without any warning.

Good Luck!

P.S. Forgot to mention, it's best to keep the tank full, even during periods of non-use, because the fuel inhibits rusting inside the tank. When the tank is partially empty, the space inside the tank above the fuel level is more susceptible to rusting.

Thanks for the advice, i'll deff be keeping the tank full.