"Checking compression would be
"Checking compression would be good, but it probably did not go bad overnight.
It is also very unlikely that the cdi is defective (although not impossible)
Does it run rough at all speeds?
Drain the carbs into a glass jar and check for water in the fuel.
If none found, run the engine and pull the plug wires off one at a time with an insulated pliers and see if the running of the engine changes. It should run worse when you pull a plug wire from a good cylinder. There will be no change when you pull a plug wire from a faulty cylinder. Hold the plug cap close to the plug and listen for the ticking of the spark. If there is ticking, then the problem is fuel related (possibly a clogged carburator jet)"