Those air cooled Rotax engines are easy to work on. Most bearings, seals etc are run of the mill standard off the shelf metric sizes & specs. The quality of the castings is, ahem, "variable" as can be seen if you ever see an unpainted engine. Some owners have made the mistake of stripping the finish off in the hope they can polish them - you can't, te casting are an inconsistent mottled finish that only looks good painted.
Kickstarting with the light flywheel is more like a recalcitrant 2 stroke, and can be very awkward.
Carburation is another issue. Several bike makers used the Rotax with all sorts of carbs = Amal, Dellorto, Mikuni etc and I don't think any of them got it right from stock! Every owner seems to have their preferred carb but I've heard Nikuni can be set up to work better than most.