I had a trainer at a job 25 years ago tell me "When you're lost go back to square one and start over.". I know myself I tend to convince myself I already know what's wrong and chase that instead of doing simple diagnosis.

A compression check will cover a lot of ground. Also, instead of carb cleaner just dribble gas down the carb and try to start it. Even WD-40 is better than carb cleaner, especially when it's cold.