I'm pretty sure the gap would not cause his misfire.
But it can be checked easy enough by setting the bike on the sidestand. When cooled down you can easily remove the right cover with only a drip or two of oil. Just place a rag under the cover and you should be set. The gasket is pretty sturdy and if you are careful it is reusable.
The hardest part about it is removing the bottom bolt on the cover. It's snug and you may have to remove the rear brake pedal assembly to get to it. Maybe you can reach it and loosen it out, but there is not enough room to pull it off completely.
