Proper Spark

Ok so I've been tinkering with my 1980 KZ650E. I don't number what the cylinder numbers are but the Second cylinder from the left side i believe is number 2. While testing the spark on my plugs i noticed that the bike will not run with out the cylinder 2 plug. It also will make no attempt to start without it. The bike will start and run without any other plug. Is this normal? Also could this have something to do with my bike being unable to idle with out choke or throttling?

If not already done, as a preliminary test, with engine running, would spray water mist onto the exhaust header pipes to see whether all cylinders are combusting.

Good Fortune!