I don't know, Clymer manual recommends Gasgacinch, which I haven't seen in years. It looks like it came from the factory with RTV silicone between the case halves. Thats what I'm scraping off anyway.What does Honda call for to seal the case halves? I suppose I could go look but the book's out in the shop and it's 93F here today. On the Continental and Lycoming flat fours it was common practice to use a thin coat of sealer and lay a thin silk sewing thread along the case flange, the thread would squash out and really sealed things up nice, never a leak.
I just got done restoring that, 1946 Logan model 820. I still need to replace the original electrical motor. It's Sam Adams time..Hey Gambler, thanks for sharing the pictures!! By the looks of the lathe in the background, this project won't be a problem for you.