My experiance from beginning to end.
Started off getting a speed bike for christmas of 2013 and wanted to put a motor on it I managed to find what I think is a Flying Horse 80cc kit on ebay for $109. After getting the engine and trying to put it on the bike in my room I quickly found out the frame was to fat for the mounts I had so I went and bought a black with red and yellow rim/tire at walmart for about $75 at Walmart.
The engine mounted perfectly onto its frame and then I found out the tank threads were bad after trying to screw on the petcock for an hour. But was I going to let that spot me? Oh, no. I went and grabbed this 1960's yamaha gas tank off an old motorcycle that was given to me (I just love old junk) and duct taped a towel around the top tube to be able to fit and hold the gas tank and then continued to duct tape the whole thing to make it look uniform. After that I set off for my first ride and then the master chainlink kept snapping off and I gave up on it until April of 2014.
After getting a new chain and some more master links I finally got it road worthy and began riding it daily well exceeding the 30min at a time break in period but going as slow as I could go with the engine pulling the bike. After about 4 gallons of gas I began riding it full throttle on the open road and it was great. Then my bad luck started to show right when my mother said "Don't ride it into town you might get stranded." well it happened alright. I was riding home on a backroad and I guess the bumps and vibrations wiggled that chain tensioner to the side and caught the spolks of the rear wheel and made it unrideable completely tearing off half the spolks and warping the shape of the rim. I walked about 5 miles since I had no phone until a friend just so happened to pass by and knew that I wouldn't be caught dead walking unless something was wrong. Good thing too because my left foot was sore and giving out since I haven't walked that far non-stop in about 3 years.
And thats about it. Right now im inbetween buying a newer but same bike from walmart because its dirt cheap right now (like $40 tops) or swapping the engine over to this old beach cruiser I have sitting in the front yard collecting more rust on its already rusted frame. All it needs is a new seat post (that actually fits because all the ones I have are too fat to fit), tubes, and its road worthy. Either way im out for a bit as this bummed me out and I have no money but am deffinatly going to upgrade to a more reliable chain tensioner when I can.