Anyone ever use one of these engines and if so how did they hold up.

I have two of them that were on my son's scooters. I have them trimed down and have a prop hub for one of them but have never tried to put a prop on one and run it. They are very strong running engines with dual rings. Probably a little heavy to. I will eventually get around to getting an EI for one and running it. I was throwing around the idea of manufacturing a twin crankcase and building a twin with the two but that never took off either. Here is a pic efore I trimmed it up.

Here is a rear pic.