My personal opinion is if you build something right the first time, you're far less likely to run into these kinds of issues. If I were to build a 212cc (not likely), I would research everything ahead of time and find out exactly what parts I needed. I'm not saying this to put you down. I'm just saying that maybe you should do some serious research, like finding out what speeds your rims/tires/spokes/hubs/bearings are rated for, and if they aren't rated for the power your engine is putting out (which some of them obviously are not), then buy parts that are rated for that kind of power. It may actually take a motorcycle wheel. A moped wheel might still not be strong enough. What you've basically got I think is something like an enduro (a class of low-powered motorcycle). However, there is a forum member whose user name is scotto, who has built a 212cc race bike, perhaps you could ask him what wheels he is running.