I have a 2000 xl1200 that has been running great all season and after a short ride a few weeks ago dropped the rear cylinder. After getting back home I checked the usual suspects, plugs, wires coil (tested the coil), coil wires, intake seals, spark, and even rockers and pushrods. During a basic "hand over the intake" compression test I found that the front cylinder had much greater suction than the rear so I felt the rear cylinder exhaust and it was drawing and blowing with every cycle. Stuck exhaust valve?

 

You've answered your own question.

 

Thanks just looking for confirmation that I'm not chasing a white rabbit.