Cylinder #2 running "cold"

Cylinder #2 on my 1982 GPz750 does not run as hot as the others. I checked by spraying water on each header after a couple minutes of warm up. The water immediately vaporizes on the other three cylinders but runs down the header on cylinder 2. It does evaporate, but not as quickly.

I checked spark and all four plugs have a nice blue spark and I have replaced the coils to brand new Dyna 3 ohm coils. The vacuum line running from cylinder 2 to the fuel petcock makes a hissing sound, could a tiny leak be causing the issue?

What other things should I check?

Hissing sound, would be a vacuum leak. Also its possible to have a bad diaphragm in the petcock, which could be causing excess fuel. Whats the plug look like compared to the others? Rich or lean?

Pilot jet, just fixed mine. Its only a .009 hole so it dont take much and the gas goes bad quickly. I buy .009 guitar string to clean mine. While youre there blow from the front air bleed to the pilot jet and to the mixture screw with it removed with carb cleaner & air. Ive had mine since it was new in 82 and ive done it a dozen times or more over the years. Hissing sound could be the vacuum line off the petcock or a hole in it but then it would only get gas in the prime position. Theres also 2 other vacuum lines on the carbs that tie into a third that goes to the emissions stuff. I hpe that is some help to you. Take the bolts out of the battery box, it gives you just a tiny bit more room. Remove & install throttle cables with the cars slid out to the right. The rest is just fighting the boots off & on and I hope they are fairly pliable or it will be a bear. A little silicon lube helps the carbs go back in the manifolds easier too. Good luck.

I fixed the vacuum leak and cylinder 2 is still running colder. So I pulled the plugs and #2 is gray and has a weird buildup on it. It looks and feels like cement. The other cylinders are all the same black.

Time for new plugs? How long since last tune-up? Which model plugs are they (heat range could be too cold)? Ed

I tuned it up just a couple months ago. The plugs were brand new B8ES, just like stock. When I switched them out I did notice that one of the plugs had the same buildup. I don't want to be replacing them twice a year, what could be causing it?

I put a picture so you can see the difference. Can't really see the buildup unfortunately

I switched out the two plugs, just between the two cylinders (so the built up one is now in cylinder #1 and a good plug is in cylinder #2). It made no difference, so I'm thinking my plugs are not the issue

You may want to try switching to B7ES plugs to see if that clears the problem. According to Kawasaki.com the 1982 GpZ 750 can use B7ES or B8ES (see diagram below). The B7ES is one heat range hotter and tends to keep the plugs cleaner. I originally used B8ES in my KZ650 because that's what the 1st edition of the Kawasaki Shop Manual called for. The plugs did not run clean, and my #1 plug would occasionally foul. All the later Kawasaki manual called for the B7ES plugs. I switched to that heat range (using ND plugs) and haven't had a spark plug issue since. Ed

I'll give it a shot. But B7ES are what I had before, and there was buildup then also. I'll still try it though