Welcome, I'm sure someone's made it work but these small motors aren't really up to the task. Most of them are half crank, meaning only one crank bearing, because they are designed for almost no radial loading. The cooling fins are small because they are designed to operate under low load. You would be served better in the long run with a purpose designed bike engine, such as Staton, Golden Eagle, one of the Happy Time variants, etc.
Welcome to MBc, you'll love it here! personally I would recomend a Happy time frame mount engine for a trek, but then again you have to think about your budget and what your going to do with it? there is so much information here, just read read read! and good luck! if you cant find an answer to your question just ask!
Im also planning on making a motorized bike. I've got 20cc (about 20cc) Weed Eater motor and I was actually working on it today. With a weed eater motor it does not have any sort of clutch, which means that when you start it, its going to wanna run away. If you make a spindle drive (friction drive) it will need to be pedal started to turn over the motor, so not having a clutch wont be too much of an issue. I know someone who has done this so I know it is possible and believe it or not he actually has the exact same motor that I have and will be using. If you have any questions feel absolutely free to PM me.
Hi Forrest. Welcome to MBc! Home of many answers, and awaiting your ideas.
General request to all new members.
Please, before posting any questions, do a search. Then READ,READ,READ.
There is a ton of information here. Many of your engine and performance issues in the Garage & Tech/Mech Help have already been covered. Here at MBc we are the home of nearly all MoteredBike questions. If you search and are unable to find your answer, don't hesitate to post your question. Were here for each other! Enjoy!
Here's a great post link to get you started. http://www.motoredbikes.com/showthread.php?t=9263&highlight=things+done+first+time