This is a conversion from Norbert Schwarze in Germany, based on a 38-series B&S
The pictures are instructive. Herr Engels added a triangular vertical support to the bed type motor mount, and tied it into the reduction drive framework with a big-ass piece of all-thread with Barry Mounts at either end. And got rid of the resilient mounts to the heads.BRIGGS & STRATON engine mount - Hans ENGELS
To equip his HM-163, Hans ENGELS chose the Briggs & Stratton 4-stroke engine converted by Norbert SCHWARZE. But it turns out that amateurs have suffered from cylinder head gaskets failures with this powertrain. Before putting this engine on his airframe, Hans first focused on analyzing the forces caused by the Schwarze frame on the B & S twin, then he made a montage of a nature to avoid problems. The following is a good example of what to do before building an accessory that is not on a plan: STRUCTURAL thinking .
All the propeller thrust, vibrations and engine torque reaction and pulsation pass through the cylinder head (and its seal), because on each cylinder head there is a silent-block <<RRY - read "Resislient mount">> located at the same height as the propeller axis.
The 2 x 2 silent blocks at the bottom carry the weight of the engine but are not sufficiently wide apart to compensate for the engine torque.
When the engine speed varies, the upper part of the engine moves laterally by more than one cm. This effort is taken up by the silent-blocks on the cylinder heads. Naturally, the head gaskets also cash this effort.
Thus the cylinder head gaskets absorb the forces due to propeller traction, engine speed variations, engine torque, and vibrations. But they are not designed for that! The Schwarze motor mount seems to be avoided.
My french is rusty so