I started building DIY motored bicycles back in the 80's, way before Chinese kits were available. I was inspired by the Whizzer kits from the 30's and later. Using the most available engines, Briggs flat heads, and bikes, Schwinn cantilever, combined with easily and economically obtained moped hubs, tanks, forks and controls, I was able to replicate a Whizzer-like ride. After several successful builds, including most with 5hp motors and one with an 8hp, I had a good stable of transportation choices. I regularly went on the Whiz-In rides throughout the years, going 50 miles or so and found them to be completely reliable.
I was re-energized when the Chinese kits came about and wanted to start building more bikes. I've always been a huge 2-stroke fan while desert racing in the 70's and 80's. I built a half a dozen or so and sold them when you could make a few bucks. After getting some unbalanced motors, and with higher prices, I lost interest. I did learn to balance my own cranks though.
Then I met Neil and wanted to start racing, so I modified one of my old bikes with higher compression. My grandson and I came in 1st and 2nd at Willow Springs, but were obviously in the wrong class because we raced against stock 2 stroke kit bikes. Jeff already had a HF 4 stroke that smoked my bikes but he wasn't signed up for that race.
Since then, I've made a 2-speed automatic transmission for my race bike and recently added variable timing.
Then I decided to make something totally different and put a back pack blower motor in a 24'' Schwinn with a go-kart clutch and homemade jack shaft.
So I don't know where I'd be in this poll because I don't use any of the popular motors. I just know I'm having a ball and don't intend to quit building any time soon.