It sounds like the classic "stuck ring in the piston", whether from an air link or lean jetting remains to be seen. If it was 20 or more degrees cooler than the temperature you normally run in, and you didn't rejet, that would lead me to the lean jetting conclusion.
The quick and easy way to test compression is to yank on the pull starter. If you've pulled it with good compression, you'll know right away if it's low.