Possible vacuum leak, now with video

I've been messing with this bike for a couple weeks when I get a chance to work on it. When I hook up the carb sync tool the #3 carb doesn't have vacuum.

At first I thought it was a clogged jet so I cleaned them, no change. Then I thought it was carb boots because when I sprayed carb cleaner on the #3 boot the idle went up. I put new boots on and still no change.

Then I thought tight valve but why would the carb cleaner effect the idle if it was a valve? I think there has to be a leak.
Where else should I check for leaks on the #3 carb?

The carb cleaner trick definitely showed a leak. As for no vacuum, you know the readings on your carb synch tool are relative to each other, right? They don't indicate actual vacuum, just vacuum relative to each other. Pull the tube off of the port and put your finger over the port, start the bike and pull your finger slowly off the port. You should feel the vacuum pull on your finger. Stop the bike, put the tube back on and then synch the carbs. You'll see the other vacuum readings change when you adjust one of them. Even if you have a large vacuum leak, the fact that the leaky cylinder is still running should mean you have enough vacuum to indicate on the carb synch tool. Try to adjust them as close as possible and then go back to finding/fixing the leak. Could be you have a small leak and the carbs are so out of synch it will make finding the leak very difficult. By opening the leaky carb more in relation to the others (by "synching" it) you raise its vacuum signal making the leak more apparent and thus easier to find/fix.
When you use the carb cleaner to find the leak, use the little swizzle stick on the nozzle to pinpoint the area you are testing and go slow, one spot at a time.

I forgot to mention, the #3 carb adjust screw has zero effect on the vacuum shown on the gauge. I tried switching the gauges around to see if it's the gauge and the problem was always on #3 no matter what gauge was on there so the gauges are fine. You can screw the screw completely out and the gauge needle doesn't move. I have #'1,2 and 4 synced perfectly but #3 is way out.

I'll try putting my finger over the port to see if I can feel anything.

Post up your bike info so everyone will know what you have. Put it in your profile signature so it comes up with each post.
With your sync gauge hooked up to the carbs, what happens when you spray carb cleaner around the offender? Does the vacuum come up as well as the idle speed still? If you do as suggested and spray with the small hose on the can, and try to pinpoint where the un-meetered air is entering. If you have the CV style carbs, square lid, these have seals on the end of the throttle shafts which can be faulty.

Oops sorry, It's a 1977 KZ1000, I'll try the suggestions and report back.

OK, the carb cleaner no longer has any effect on the idle since putting on the new boots.
I put my finger over the port and I could feel vacuum.
I was told the #2 carb was the carb to sync all the others to, is that correct?
Here's two video of the bike running. In the first one I pull the spark plug on #3 and the bike almost dies.
Also, forgot to mention, the #3 pipe is a lot hotter than all the others.

Perhaps the synch adjust screw is stripped out. This is the screw inside the top of the carb, right?
On Kawasakis, there isn't normally a baseline carb that the other carbs are synched to, like you would see on a Honda. You synch 2 to 3 then 1 to 2 then 4 to 3. You'll see the other carb vacuums change when you change one of them so you just repeat the sequence and dial them in.

I've been syncing them wrong then. I've been Syncing them to #2 thinking it was the baseline carb. I'll try to sync them the way you suggested tomorrow.

Something you might have not noticed.

The adjustment screw on #3 has zero effect on the adjustment of the carb. You can screw it completely out and the gauge doesn't change. If I were to follow your suggestion I would basically be syncing all the other carbs to #3.

I'm not saying I won't do that but I'm asking, does that make sense?

That really does not look right. Are you positive that the little vacuum port on the #3 carb holder is not plugged up or cracked from the holder? Can you tell if cylinder 3 is firing (does exhaust header get hot the same time as the other pipes?) If you have a spare spark plug handy you may want to try this to see if #3 is firing: Pull the spark plug cap off #3 plug; plug the spare spark plug into the cap; rest the spare spark plug on the engine so it's metal body is grounded; start the bike and see if it idles or runs any differently now that you know for sure #3 is not firing. If the engine idles and runs the same #3 was not firing in the video. I would then check the compression. Ed

Whats the compression? that sounds like compression escaping in the first video. You might have a burned valve, or a bad head gasket. Do a compression and leak down test.

The pipe on the #3 is hotter than the rest. So it's firing. In one of the videos I pull off the #3 spark plug wire an the idle goes down, the bike almost dies.