Well now, we have a bit of a frustration over this ooopps it fell off.
Sorry to see such a thing. I would send it back for a replacement and tell them the truth of the fact, this was a faulty casting and the mount wing failed on the first trip. And when you get the next engine, try to modify into the mounting a rubber dampner to absord the vibration.
When i was a kid, we use to do everything under the sun to get our early B&S units to mount up to our bicycles, and the incorporation of rubber dampners was the key to a good sturdy ride.
Good luck on the next build. I for one have gone through over 15 different small bore engines in the past years. Most of them suffering detination from introducing nitro-fuel to them and running them too hot. As a kid trying to re-invent an early style of motor-biking, you tend to over do everything.
I like to go fast and like to push the envilope on the small and micro enginies we are using today. Nothing beats the feel of achievment before the whole mess just erupts out from under your kiester.
Best part of this fad, I am 50 and still doing the same crazy stunts with my younger kids and their friends. And they always come back for more.