Just picked up a 1986 ZL600 that has low mileage but consequently has been sitting for a while. At first it would only run on two cylinders, but after a two or three mile ride the third one perked up. I drained the tank of fuel and refilled with Hi Test gas and some Sta-Bil (gas stabilizer) and Marvilous Mystery Oil. The bad cylinder is on the outside so I opened up the carb bowl and diaphram and it is very clean, spark plug is firing well, good compression. If I leave the choke on for a while the exhaust pipe will began to get hot (cylinder firing), but if I do not choke past normal warm up that cylinder's exhaust pipe stays cool. Any Ideas? Maybe I just need to take it out and jun the ---- out of it?

 

Sounds to me like a clogged pilot jet. I realize you said the carb bowls are clean but are the jets cleaned? With this age bike, unless its been stored properly, may have some carb cleaning needed. A very good carb cleaning

 

Yep; +1^Z. It doesn't take much to gum up those little jets. I'd probably advise against the "run the .....out of it" approach.

 

Oh; forgive my manners. Welcome to the forums, DJ. Glad to hear you're getting some vintage Kawi back on the road!
Gear up; stay safe.