First start 1980 KZ750 h1

Well started up but one side has white smoke cylinder 4 its not smoke it like w vapor but one thing its cold on the exshaust or warm checked for spark okay what that usually mean...can it be the carb please help just took two months to rebuild

Also its got compression just checked

Meaning don't seem like 4 is firing but have good spark

Compression and good on the leak down

If it has good compression and good spark, then the problem most likely resides on the intake side.