MVVS is still very hush-up about the engine.
It is a 43cc stroke crankcase with a blown-up cylinder.

The nipple up front is so the factory/user can apply extra lubrication for the front bearing and seals.
When in Nürnberg at the Toy fair, several engines were equipped with this feature, along with increased play between crankshaft and crankcase.
If you study their flyer leaflet closely, you can see it at http://www.mvvs.cz