dead cylinder worries

Well, I started my bike for just the second time since a full carb rebuild and discovered to my dismay that it has a dead cylinder.
On the first startup since rebuild, it fired right away and ran on all four.
It idled way too high, around 2000 rpm.
This time I turned the pilot screws in a little and when it finally fired (it is hard as hell to start these bikes on 3 cylinders) I eventually found that #3 cylinder is dead as a doornail.
I found that out by pulling the plug wire on #3 while it was running.
It ran just the same way without #3 wire connected, so I found the culprit.
The depressing part is that I pulled the plug wire and found it sparking like mad.
Next I pulled the plug and it did look a bit dirty from unburned gas.
I figure an outside chance that the plug is fouled from the engine being cranked over so many times before starting.
Next I checked for fuel in #3 carb by opening the drain screw and found gas pouring out.
If the engine hadn't been so hot I would have pulled the cam cover to see if the cam took a dump.
It looks like a compression check is next, though I don't have a compression tester that would fit down into the plug well.
Does anyone know where I might buy or rent a compression tester that screws into the plug hole?
Any help would be appreciated.
I was all psyched up to tune the bike and ride it...now this.
I need a beer or six....

 

How many miles on yo be-ach??

Screwing in the mixture screws is not the way to cure a fast idle; your synch is probably in need of adjustment or throttle cable binding, or idle speed screw fouled up.

try UNscrewing the mixture screw on that cylinder as you may restore running condition....try 3 turns out from closed.

if u suspect a fouled plug, switch it with one from a running cylinder.

If bike ran on all 4, it's very unlikely that you have low compression in one cylinder.

 

why not go buy some new plugs and make sure there is not a loose connection its sounds like should be something simple compresion check tool?? northern tool lowes etc may have one ....if the float is sticking may be flooding it ouch carb rebuilds always so much fun...............

 

could be a sych problem

Thanks for the tips.
I'll back the pilot screw back out and fire her up again.
Also, I have a spare plug that I can try.
I haven't vacuum synched the carbs either, so it could be the throttle plate is not open enough to give that cylinder some air.
I suppose I could back out the idle screw on #3 also.

 

mileage

Also, the bike has 19,500 miles. She's getting old.