Something that commonly happens to these engines (and the Honda Twins and Singles) when they sit for a long time is: light rust on the valve faces. When they are then started up they may burn oil from the uneven compression, so lots of folks think it is "stuck rings". But, "stuck rings" also equate to an engine that will not run over, so that is the distinction.
In these cases I check the valve clearance first. If the clearance is found to be larger than normal (it often is), LEAVE IT THERE. This is needed because that symptom is telling you that the valve is not seating all the way, so it likely has rust or crust on the valve face and/or seat. The "good news" is: Honda's SOHC4 design will wipe the rust away from the valve faces in less than 100 miles. THEN go in and check/set the valve clearance.
At my bike shop, in the Spring, we used to get bikes like these that would not start, caused by this issue. In those days I lived in an area where it was 100% humidity much of the winter, which caused the problem if the owner did not add oil to the gas for the final tank of fuel before winter storage. Usually, the bike just got parked, MAYBE with a cover over it, and then in Spring the battery got jumped to try and start it. Then it came to us with low compression in typically 2 of the cylinders, a sure sign of valve-face rust. I enjoyed "fixing" these bikes because it meant I got to ride that bike for a few days to 'fix' it, running it with oil in the gas until the normal power level returned and they would idle again, after which I'd tune them up and make good $$ from the week-long effort.
