leaking vacuum petcock

Hi all, I have a very slow leaking vacuum petcock on my 85 900 ninja that is constantly contamination my oil. It leaks 1 drop about every 2-3 minutes (so about 30 drops an hr or 720 drops a day) and I am tired of changing oil every month when its still clean. I rebuilt the valve last year and I guess I did something wrong, just dont know what. Are there any rebuild kits better than others? Has to be the o ring or the spring to hold it in place that is weak. Any thoughts? Thanks in advance, Joe

jaguar wrote:

Hi all, I have a very slow leaking vacuum petcock on my 85 900 ninja that is constantly contamination my oil. It leaks 1 drop about every 2-3 minutes (so about 30 drops an hr or 720 drops a day) and I am tired of changing oil every month when its still clean. I rebuilt the valve last year and I guess I did something wrong, just dont know what. Are there any rebuild kits better than others? Has to be the o ring or the spring to hold it in place that is weak. Any thoughts? Thanks in advance, Joe

Might also be the petcock valve gasket. Here's a link to the petcock repair kit available through Z1E.

'85Ninja900 Petcock Kit

One or more carbs may be leaking at float needle/seat interface and thereby allowing continuous flow into floatbowl. Excess fuel is usually allowed to escape via overflow circuit routed through tubes onto ground underneath the bike. But where overflow circuit is blocked (by crud, pinched tube, etc.) the excess fuel may rise up into carb throat and from there make its way into the crankcase. Any deficiencies in these areas should be corrected along with the petcock issue.

Good Luck!

Thanks for the info. I agree it shouldn't make it into the intake throat so I will work on the overflow circuit. I have waisted 8qts of oil in less than 500 miles. I will drain the tank and remove the valve and rebuild it. Then I will get the floats to close the needles. Thanks

if the gas is getting in to the crankcases that is usally a sign of weak or scored needles and seats [float valves] i would start there then worry about the petcock after and by the way you probably didn't do anything wrong with the kit it's just the way the fuel is nowadays it contains additives that are really hard on rubber products i see this kind of thing happening more and more all the time.

jaguar wrote:

Thanks for the info. I agree it shouldn't make it into the intake throat so I will work on the overflow circuit. I have waisted 8qts of oil in less than 500 miles. I will drain the tank and remove the valve and rebuild it. Then I will get the floats to close the needles. Thanks

Floats could be okay (bouyant and not leaking) and already set at correct heights. As noted by timebomb33, would first suspicion float needles and seats, which are often corrected with a good cleaning. It's best to keep each needle with its same seat in the same carb (and not mix the needles around).

Am thinking the needles here have rubber tips, and concur that they may have deteriorated and may need replacing.

Z1E lists a six pack of float needles under the 1985 Ninja 900 category, but I don't see the ZX900 specifically listed among the several models and brands using these needles. So if deciding to replace, it would probably be best to call and verify with Z1E before ordering. Here's the link> Z1E Float needles

If not already done, would install an in-line fuel filter to help keep the float needle/seat interface clean and clear of foreign crud suspended in the onslaught of incoming fuel.

Z1E Inline Fuel Filters

Good Luck!

In rebuilding your petcock you most likely got a K&L kit, here is a problem I had with that kit.

K&L petcock kit

Ordering OEM diaphram (which includes plastic spacer) for $12 cured my problem, seals perfect.