By using the flathead instead of overhead engine, we could make the engine smaller despite the big cubic capacity.
With the flathead we could make it much simpler and do not have the complectity of the rockers. One of our custumers wrote on a blog after exploring the inside of the engine " This engine will go a long way. After fiddling in it's belly, I have even more faith in the mechanics of the engine. It is so simple, there is not much that can go wrong."
The extra weight of the cooling liquid is compensated by the the flathead design, as we do not have the overhead parts with cooling ribs. The liquid cooling makes it possible to practise "touch and go's" without any danger for thermal shocks or hotspots. It further improves fuel efficiency and lowers emissions.
We choosed for big cubic capacity (resulting in a high torque, and direct driven, because we feel more comfortable with a big engine running lower RPM instead of a smaller engine running high RPM. We took one of the good points of high RPM engines by choosing for nikasil treatment for the cylinders. This expensive treatment is used for motorbike engines running up to 12.000RPM. At a red line of 3000 RPM this treatment is an extra guarantee for a long life.
When a valve of an overhead engine is not closing, the engine stops and expensive repair is the result. When a valve of a sidevalve engine is not closing, you continue flying with less power and there won't be expensive repair cost.