Cold cylinder, miss after warm up.

This is a 79 ST with 28 pumpers from the best carb guy on the planet,WGC.
Problem; After warming up....2 min., or more the #2 cylinder consistently is 50 degrees colder than the other 3. Compression on all 4 is in the 120 range. And only 8400 miles on it. Some of the vacuum parts are missing so I duped them back and haven't tried since .....any input? I'm duped!!!!

Gorgeous bike!!

Too tight valve clearance can permit acceptable compression and combustion until attaining normal operating temperature which then results in valve leakage and failed combustion.

Perfect carbs can't compensate for insufficient compression at normal operating temperature.

Good Fortune!

What vacuum parts were missing?

Someone had connected the valve cover vents together, and the large vacuum piece that connects them to the air box is missing, and the 1&4 intake boot tubes were blocked off with a screw.

Thank you for all the help, Patton ,you are correct with your response, And I will dig deeper and check my clearances. And I will post my findings.......All you guys are better than a factory manual......by far....
Kaw corral.

kaw corral wrote: Someone had connected the valve cover vents together, and the large vacuum piece that connects them to the air box is missing, and the 1&4 intake boot tubes were blocked off with a screw.

It's common practice to remove the stock "clean air" paraphernalia.




Good Fortune!

I am not sure just where the port to provide vacuum to the petcock is located on this bike, but it is is on #2 then I would look at the petcock. There have been posts here and on other sites that have indicated that a tear in the diaphragm in the petcock allows fuel to be pulled up into the carb or carb holder into #2.

Once again thanks to all of you Kawasaki enthusiasts for your help ......the reason.......all the valve clearances with the exception of #4 int&exh. We're to say the least so tight I couldn't even get a .0015-.002 feeler gauge in them.......stone cold....they obviously have been shimmed too tight at some time......
Thanks Patton for your input.
Kaw corral

Actually, the lack of clearance suggests that they have not been shimmed at all. This is a very common problem as too many owners are too afraid to do it themselves and too cheap to pay. The valves pound their way deeper into the head, slowly reducing the clearance until there is none. Then burnt valves.
You will want to plug the hole in the air box and insure that the plugs on the carb vacuum ports are soft and sealing well.