I know mine's a different engine, a 602 with afterglow, but in the owner's manual it says that a rough start cold is normal and to rev the engine until it runs smoothly.

I'll check my 603 manual today, I'm curious whether it suggests same.

I didn't at first subscribe to reving the engine cold, prefer putting it under load by putting it in reverse as soon as there's normal oil pressure (seconds), but the realization that a missing cylinder is fuel spraying onto cylinder walls is what leads me to follow the recommendation.

When plugged in I have never had a rough start, but when sitting out in a parking lot it sometimes does. Rare as mine is mostly a fair-weather ride, but waiting a little while after the light goes out as some on this site suggested seems to cure that also for me usually (hasn't been in sub-10F).

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Gone to the dark side

- Jeff