Re: Rider engine adapter plates
I believe there is an O-ring that goes between the adapter and the engine, pretty sure that Kohler has a roughly 2.5" diameter ring on the rear closure plate that seals against the adapter. I suspect RTV will work fine.
The Kohler 18 hp you have from a Cub, is it horizontal or vertical? If it horizontal, it is a M18. Pictures please?
When GRAVELY switched to improved Magnum 18 and 20 engine, Kohler made the engine to bolt directly to the GRAVELY trans axle. The rear closure plate on the GRAVELY version of that engine IS the adapter. There is no separate adapter on the later tractors.