Gas not getting past the petcock

[ZeroG]

I'm currently fixing up a 1993 zx600 that has been sitting for the past 5 years. I've cleaned the carbs and rusted tank and cleaned/rebuilt the petcock. It starts right up if I pour gas directly into the carbs, but for some reason, it won't draw gas out of the tank.

I've tried it with the tank partially filled with the petcock on reserve and fully filled with the petcock on normal, neither of which worked. Replacing the gaskets and vacuum diaphragm in the petcock hasn't made any apparent difference (except that it no longer leaks).

I'm completely stumped! Any help would be appreciated.

[SabreValkyrn]

This is the bike from: Is this bike worth the chance?

Valves adjusted, carbs cleaned, and oil/coolant changed.

The bike sounds really smooth and wonderful when it starts.

Stock everything from what I can tell, even Dunlops.

By-passing the petcock results in an almost instant cold (or warm) start.

With the petcock, we are able to get it started if the choke and throttle are completely open.

[CynicalC]

Reattach vacuum lines correctly? Check for obstructions in vacuum line? Try actually running it and check for vacuum with a gauge?

[Jesse8931]

you can remove the spring in the petcock but fair warning it will flood your bike out if the motor is not running you have the fuel on.

[Motofool]

Have you cleaned the mesh filters that go inside the tank?

[SabreValkyrn]

Originally Posted by Motofool

Have you cleaned the mesh filters that go inside the tank?

Yes, we removed the normal/higher one because it was so crusted and filled with rust. There is an inline fuel filter, so we were advised to just take off the petcock mini-filter.

[Motofool]

Open the gas tank cap and blow backwards in normal and reserve position.

You should hear plenty of air bubbling inside the tank.

Connect a long hose the outlet of the petcock and make a U shape, blowing from a point well above the level of the fuel.

[gitoy]

is everybody in agreement that this whole petcock issue is hands on dirty?....bwahhaha...

[sLick415]

Put a tube on the vacuum port, suck on it and see if gas starts flowing.

[Motofool]

Originally Posted by ZeroG

.........I'm completely stumped! Any help would be appreciated.

Any updates?

[cuong-nutz]

http://www.sportbikes.net/forums/zzr...-gone-out.html

I suspect the fuel pump to be out. Make sure the solder joints are not broken/corroded.

[Jesse8931]

Originally Posted by cuong-nutz

http://www.sportbikes.net/forums/zzr...-gone-out.html

I suspect the fuel pump to be out. Make sure the solder joints are not broken/corroded.

its a 93 no fuel pump

[cuong-nutz]

Originally Posted by Jesse8931

its a 93 no fuel pump

ah.... Must be thinking of something else

any updates @SabreValkyrn, @ZeroG

[SabreValkyrn]

Originally Posted by cuong-nutz

ah.... Must be thinking of something else

any updates @SabreValkyrn, @ZeroG

Thank you all for your replies, the bike is 85 miles from me and 180 from ZeroG, at a friends house. Given Mother's day, we aren't able to work on it this weekend. I think Zero is going to work on it on Wednesday.

[ZeroG]

Yep, that's the plan at the moment. When I get back up there, I'll run through all your suggestions and see what happens.

And Cuong_nutz, don't scare me like that

[ZeroG]

Okay, everybody. I've just spent the past couple hours tinkering with this issue again.

When I got here, I noticed that there was a little gas leaking out of the petcock. Further inspection showed that it was leaking from the knob-side of the petcock. Also, when I turned the petcock to On or Reserve, gas would dribble from the outlet (with no vacuum).

I took the whole thing apart again, used gasket sealer on all the gaskets, and put it back together. It no longer leaks or dribbles, but there's still no flow! I tried sucking on the vacuum hose and hooking it up and starting the bike with no success.

I also noticed that when I started the bike, I had to use the choke (not unexpected), but if I gave it any throttle, it died immediately. I don't know if that's connected at all, but I thought I'd mention it.

This is driving me crazy!

[cuong-nutz]

Originally Posted by ZeroG

Okay, everybody. I've just spent the past couple hours tinkering with this issue again.

When I got here, I noticed that there was a little gas leaking out of the petcock. Further inspection showed that it was leaking from the knob-side of the petcock. Also, when I turned the petcock to On or Reserve, gas would dribble from the outlet (with no vacuum).

I took the whole thing apart again, used gasket sealer on all the gaskets, and put it back together. It no longer leaks or dribbles, but there's still no flow! I tried sucking on the vacuum hose and hooking it up and starting the bike with no success.

I also noticed that when I started the bike, I had to use the choke (not unexpected), but if I gave it any throttle, it died immediately. I don't know if that's connected at all, but I thought I'd mention it.

This is driving me crazy!

Sounds like the assembly of the petcock is not correct. When vacuum is pulled from the petcock, gas should flow.

[Jesse8931]

again removed the spring and try again

[ZeroG]

There still isn't any flow even without the spring in the petcock. I also took it out of the tank (again) and tried putting water through it while sucking on the vacuum line - still nothing.

So the tank and carbs are not the issue, it's definitely something up with the petcock. I can't think what else to do but just try and find a new universal replacement or something.

Any last bright ideas? By the way, thanks for all the help so far!

[ZeroG]

I pulled out the diaphragm as well and capped off the vacuum nipple. That basically makes it into an expensive shutoff valve, which works... kind of. It flows fine now in the On and Reserve positions, but obviously it's not controlled by vacuum, and I'd have to shut it off every time I stop.

[ai4px]

Originally Posted by sLick415

Put a tube on the vacuum port, suck on it and see if gas starts flowing.

Nice to know you can suck start a ninjette. What a happy little motorcycle.

[ZeroG]

Yet another update:

The vacuum-less petcock is now installed on the tank. The fuel flows fine when the hose and filter are not attached to the carbs (just dumping it into a gas can). When I connect everything, however, the fuel doesn't flow at all.

The only reason I can think of for this is if there was a blockage in the carbs, but not only did I clean them, the fuel gets down fine when we run it straight in from a gas can.

So from all the tests I've run, everything works fine by itself, but together there's still an issue..........

[cuong-nutz]

Maybe the vent on the carbs are clogged?