Building the Affordaplane Part 39 

I’m not Jon, but it appears that harbor freight has the one that Jon is using. I have one that more closely resembles the unit available from wholesale tool.

You probably won't get anyone to give you confirmation to use anything, due to potential liability issues. But just know that when it comes to ultralights, so long as it is done within the legal framework and done in a safe manner, go for it at your own risk as you seem appropriate. Also, experimental category aircraft gives you similar freedom to try things. But you still need to follow the applicable laws there too and get an airworthiness certificate, have a pilot's license, etc. Just know that many ground vehicle engines don't have thrust bearings on their crankshafts like airplane engines. Airplanes pull along the rotational axis of the crankshaft, and car/bike engines have their loads applied perpendicular to the rotational axis of the crankshaft. This can result in failures of the crankshaft if it's not used the way it was intended, or modified to take that load (Corvair 5th bearing for example). Of course there have been a number of automobile and other ground vehicle engines used successfully in aircraft. But there probably wont be anyone with knowledge of the specific engine you have in mind. We maintain safety in aviation by being smart, being reasonably cautious, and not taking unnecessary risks. If you're ever going to try something new or experiment with something, take the time to develop a plan, and think through what might go wrong and how to deal with it safely. Seek out help from those in your community with greater experience and knowledge. Test things in successive steps, don't be impatient or impulsive. Get some training in engineering design, read books on the types of things you wish to try, get some flight training, learn the applicable regulations, etc., to increase your odds of success. When in doubt, don't do it, defer to others, etc. But being reckless in aviation tends not to end well in a hurry.