Yet another petcock question

Today I decided to try and adjust my idle mixture since it was a little rich. I can do this without removing the tank thanks to my little screwdriver I made. I did exactly as the manual states with turning them in and backing them off 1.25 of a turn. Started the bike and while adjusting, the petcock started squirting some fuel out. Not a steady stream, but with the vacuum pulse of the motor. It is the original vacuum unit and has not given me any trouble before. The bike runs better now but it's getting gas on it. On the unit there is a small hole coming from the valve portion on the far side. The plate on top of that (plastic) has a groove cut in it to allow passage to the outside. That's where is it coming from.
What is that for and why did it start? Should I just plug the line and get a new gravity fed petcock? I also put the vac line on another carb and it had the same problem. I left the bike off for about 10 mins and when I tried to crank it again it was flooded.
Any ideas?

You can usually find rebuild kits relatively cheaply. If this is for the '98 Police 1000 in your signature, I'd probably try to get a rebuild kit for it. Some have success rebuilding, some don't.

I like stock stuff, so I'd give the rebuild a shot first. If you don't mind switching to manual operation, Jeff's got some cheap adapter plates and petcocks over at Z1.

Check out Jeff's petcock writeup at Z1 Enterprises . According to his writeup, rebuild kits will fix 50-75% of petcocks. The rest are beyond repair, so if you don't mind the manual operation (BLOCK OFF YOUR VACUUM PORTS!) and want guaranteed success, go with the manual one. If stock is important, try a rebuild kit first, but be cautious as it might fail on you.

Also, it sounds like the rubber diaphragm might have failed. You might want to check your tank for internal corrosion and consider cleaning it thoroughly if it's rusted at all. It's possible that somehow a piece of rust made it into the petcock body and made short work of your diaphragm. You might consider installing an inline fuel filter to prevent particulate matter from making it further into the carbs where it'll cause more problems.

I've got one of Jeff's petcocks on my police bike and I like it fine, and it works, period. It's an off, on, reserve. The vacuum driven petcock doesn't force more gas through the line. You'll get plenty of gas using the replacement petcock. I'll have to look at my old petcock to see what you are talking about but it sounds like the rubber gasket has punctured or something.

When I get home I'll look at my old petcock to see if I can figure out what you are talking about. I don't remember having any other port on it or groove cut in it that you are talking about.

I figured out a way to make the old petcock into an On, Off petcock by replacing the spring that activates the shutoff with a piece of rubber vacuum hose. This kept the vacuum port turned off when the petcock was in the ON position, and allowed it to work in the Prime position only. My only question was whether the prime position draws gas from the lower or Reserve part of the tank. This would eliminate having on and reserve, but with a fuel gauge, that shouldn't matter... You might give it a try... I had to experiment with the length of the vacuum hose piece I cut to get it exactly the right length but it worked...

The vacuum when applied sucks open the valve that is being held closed by a very weak spring, just strong enough to close the valve when no suction is applied. So replacing this spring to force the valve to stay closed is easy to do...

(I very much like being able to shut off the fuel line!!! I now have my floats adjusted right and new float needles, but when parked, the bike leans over quite a bit, and if a tiny piece of crud sticks in one of the float needles, you're going to have a puddle under the bike, and no telling what else. I'd rather have it shut off.)

Post edited by: fergyfer, at: 2006/01/16 16:04

The groove he's talking about is on the back side of the square plastic piece that has the diaphragms. I think it's to let air move in/out to fill the gap between the diaphragms. It leads to the outside -- if you look at the exposed plastic edge on your OEM petcock, you'll see a small hole that's actually the end of this groove.

Unless I've misinterpreted, but that's the only one I remember seeing.

I pulled my old one apart and verified that the groove cut in it must be for air. Meaning that if gas is coming from there your diaphram is punctured.
I also verified while I had it apart, that the mod I mentioned above will work and does draw gas from the reserve port only. In my opinion, that's what I'd want if I modded this petcock, since we have fuel gauges on the bike. It would also eliminate needing to repair the damaged diaphram as it would never come into play with the vacuum port blocked. Just a thought, but if you want to save a few bucks and use the old petcock, the mod would work.

Float needles and float seats are primitive and if a bike is not running, they WILL leak unless gas is turned off. With a gravity feed petcock, the onus is on the operator to turn the gas off when the bike isn't used. The vacuum actuated petcock is an attempt by Kaw to eliminate the need to remember to turn off fuel. The trade off is that it is more complicated and relies on an extra line (vacuum) to actuate a diaphragm (you have seen it go bad). I prefer gravity petcocks as they are simpler and less prone to problems except, of course, operator error (not turning off). Measure the bolt offset on your petcock, order an adapter plate and replacement gravity feed petcock and be done with leaks. Don't forget to remove the hose connected to your carbs and put a vacuum cap on the spigot on the carbs else they will draw in air and not perform as they should. www.z1enterprises.com can help with the parts.

can't you just plug the vacuum line and just turn the petcock to the prime postion instead of buying a new gravity fed petcock.

You could.. then turn gas to "ON" to shut it off. Just don't know if the diaphragm will leak as it may be doing in this case. Lordy... a Custom Chrome single spigot petcock costs less than $20 and is totally rebuildable. The adapter plate is only about $30. Live it up and spend the bucks!

Petcock and adaptor plate from Jeff total under $30...
They work like a champ. You need the part, Jeff needs the money, sounds like a marriage made in heaven.

fergyfer wrote:

I figured out a way to make the old petcock into an On, Off petcock by replacing the spring that activates the shutoff with a piece of rubber vacuum hose. This kept the vacuum port turned off when the petcock was in the ON position, and allowed it to work in the Prime position only. My only question was whether the prime position draws gas from the lower or Reserve part of the tank. This would eliminate having on and reserve, but with a fuel gauge, that shouldn't matter... You might give it a try... I had to experiment with the length of the vacuum hose piece I cut to get it exactly the right length but it worked...<br><br>Post edited by: fergyfer, at: 2006/01/16 16:04

Today is the first day that I have had a day off and not be sick so I tried it and it didn't work for me. Gas came out of the air port even better. I figured the gasket needed to be thicker so the diaphram would seat tightly on the plastic part. That helped but still leaked. Jeff is out of the regular valves right now so I think I'm just going to try a rebuild kit.