Won't run

Hello.  I just joined the forum and this is my first post.  I have a 1981 KZ440.  I have had it for about 25 years and it has been a flawless performer until las spring.  After sitting idle over the winter, it would only run on one cylinder.  Here is what I have tried:
1)  Changed plugs -  no difference
2)  Checked compression - 136 psi in both cylinders
3)  Checked spark - good spark at both plugs
4)  Cleaned gas tank
5)  Removed carburetor and spray cleaned everything I could reach and tested floats
6)  Removed disassembled leaking fuel petcock, cleaned and reassembled - still leaks

None of this has made any difference.

I am fairly certain that this is a fuel problem.  I want to replace the leaking fuel petcock but I am having a hard time finding the correct one.  My model is KZ440AE and I can not find any reference to the "AE" designation online or in my Clymer's repair manual.  Can anyone shed light on that?  My petcock has two ports, one for fuel delivery and one for vacuum to one of the carbs.

Any help or advice will be greatly appreciated.  I am a novice working on a motorcycle engine.  I'm an antique car guy so I work on those all the time but this is a new experience for me.

Thank you,  Barry

 

Had the same thing happen last year.

Disassembled the carbs completely.
Soaked in Berrymans carburetor Chem Dip.
Blew out all passages with compressed air.
Bike is fine now..

I also use small amounts of Techron for detergent as I currently don't use top tier gasoline.

When running spray starting fluid in the airbox to see if the dead cylinder comes to life. That would possibly point to fuel delivery.

There is no AE model. I suspect you are looking at the engine number. The frame number will tell you which model it is.
In 1981, there were three--
KZ440A, chain drive LTD
KZ440D, belt drive LTD
KZ440B, chain drive standard

The petcock leak is likely because of perished rubber bits. They need to be replaced and the valve seat needs to be carefully polished.
As already noted, the only way to get carburetors fully clean is by a complete disassembly and very carefully insuring that every tiny passageway is clear. All the rubber bits, except the slide diaphragm, need to be replaced, too.