As a minimum on the Saito, I would remove the carb/Backplate. Muffler, and the valve covers. You reall y should take the Cylinder jug/cam box off. Otherwise it will be a problem getting the antifreeze out of that area. If your bearings are bad, cleaning the engine will not make them good.

I don't remember just how the Enya is made.

Personally, I would clean the outside of the engine with brake cleaner and forget the antifrezze in this one application.

Jim