Gas leak possibly the petcock?

Ok, I've had my 78' kz650 for a few months and just signed up here.

Anyways, the bike runs great, good cold start, carbs seem to be fine for the most part, runs a little rich down low but fine about half throttle. But, when ever I hit the kill switch within 10 minutes or so the #2 carb drain squirts a little bit of gas out, and does it intermittently until I start it up again. I ended up putting a little bucket underneath the drain hose overnight and a good quarter gallon was in there.

The Haynes manual I have goes into detail about a petcock with an off position. Mine has reserve, prime and on. So, I thought there was a seal missing or something because the little piston is supposed to only open when the engine is running. But when I took it apart I couldn't find any damage to the o-rings, diaphragm or anything.

I'm really confused because I can't figure out whats going on with it. If anyone else has any ideas I'd be happy to hear some.

Thanks,
Trent

Your bikes petcock is vacuum operated, so under normal conditions (except when on "PRI") it should only flow when the bike is running.
The o-rings and diaphragm may look OK, but it's not always those parts that fail. Sometimes what happens is that debris will make it past the screen filter inside the tank and into the petcock, which if abrasive enough will wear a pattern or gouge into the petcock cast body itself. And nothing will fix that type of leak, so a new (or known-good used) replacement petcock are your best bet here.

Now onto the leaking carb.
The float needles and seats within the float bowls are designed to stop the fuel flow into the carbs when a specific set level is reached. If one (the #2 in this case) doesn't seat fully, it will continue to flow fuel into that float bowl and run out of the overflow outlet fitting on the bottom.
Long story short is that you're probably going to need to remove the carbs, disasemble and clean them, and also check that the float needles aren't worn or gouged and preventing them from stopping the fuel flow.

Personally I would use that Haynes manual to line a bird cage with, as the descriptions and procedures in it tend to be slightly vague at best.
If you check on eBay Clymers manuals, or better yet FSM's show up there quite often, which IMHO are much better in describing repairs thoroughly.

Also check the filebase here on the site, as some specific bike manuals are listed there that can be downloaded for free.

Ok not the answer I was hoping for. Thought super glue was gonna be a possible solution. (sigh) Oh well.

One question though. If I can fix the petcock or replace it then more fuel won't flow into the carbs, right? So I won't have to mess with the carbs hopefully?

Thanks for the quick response though.
Trent

If you replace the petcock with one that functions properly, yes, it will prevent fuel from flooding the float bowl when the bike ISN'T running.
HOWEVER if the bike IS running, it will continue to flow fuel into that bowl because the float needle isn't shutting it off when it reaches the set level - it WILL start to leak slightly, most likely only when at idle though.

So basically you will need to remove the carbs to give them a decent cleaning, and to check why that float needle isn't seating properly. It could be as simple as debris stuck in there and causing the leaking problem.

It's really not that hard to remove and clean the carbs on these old bikes.
If you've got a manual (a FSM or Clymer manual preferably), a digital camera to take pics so you know how things go back together, and take your time, you should do just fine.
If you do end up having problems or questions tackling this, there are enough folks here who have done this on their own bikes numerous times and will gladly walk you through it.

Post edited by: RetroRiceRocketRider, at: 2007/08/22 16:02

Well, I never thought about that. Certainly don't want gas all over the place while I'm running it.

I just started taking apart the carbs a few minutes ago. I figured I needed to clean them anyways and saw the carb cleaning thread the other day and I was intrigued by the lemon juice method. It sounds cheap, easy and effective.

I checked the float needle and it was fine but the little tang needed to be adjusted connected to the floats. There is some debris in the bowl so that might have been a factor as well. They're overdue for a thorough cleaning anyways.

Other than that thanks so much for answering my most likely newbie questions and wish me luck.

Trent

Well, I never thought about that. Certainly don't want gas all over the place while I'm running it.

I just started taking apart the carbs a few minutes ago. I figured I needed to clean them anyways and saw the carb cleaning thread the other day and I was intrigued by the lemon juice method. It sounds cheap, easy and effective.

I checked the float needle and it was fine but the little tang needed to be adjusted connected to the floats. There is some debris in the bowl so that might have been a factor as well. They're overdue for a thorough cleaning anyways.

Other than that thanks so much for answering my most likely newbie questions and wish me luck.

Trent