The Johnson 115 on my RIB has a slight misfire. It only happens when idling, but if you knock the motor back to idle for any length of time at all, it misfires on 1 cylinder slightly, and smokes a bit too, open the throttle a bit and it quickly clears and runs perfectly at anything over about 2000rpm with no smoke at all. Doesn't matter if cold or hot, same thing.
I don't know a lot about 2 stroke engines, and particularly oil injection ones, is this a common thing? The 2 stroke lawnmowers Dad used to own usually ran like a bucket of bolts at the best of times and the strimmer I have - also 2 stroke - is equally temperamental!
Is it likely to be just a bad plug, or something to be more concerned about? As I say it is fine once you open the throttle a little. I'm going to get a new set of plugs for it anyway as they look to have been in there rather a long time, but I just wondered if there is anything I should check.