These little guys are sold in the millions all over China and the rest of the world. Mind you, this one has a few modded parts but the basic engines remain the same. These are small displacement 66cc(sold as 80cc) engines with no transmission except for a simple friction clutch plate. They're sold in kits on ebay for extremely cheap and they have mounts to attach to a bicycle to allow you to motorize your bike!!
In the real world, I started with the standard engine and mounted it via direct drive to a hard tail mountain bike frame. It was fun for a while but soon enough I wanted more. So I ended up building a custom frame(model to come) with suspension and jackshaft kit and freewheel crankset to run the motor through the gears. This essentially means that I used my bike gearing as the transmission allowing much better gear ratio's for climbing and speed.
The cool part about this model is that it's 100% accurate so you can use it as a place holder for your motorized bike project, build it in CAD and not have to worry about fitment come fabrication time!
Modeled with Solidworks, rendered in Keyshot.
In the ZIPPED file package, you get everything shown in the pictures and more. The file formats are .sldprt and .asm. I did not include .step or .stl files but if you have CAD software, it takes just a few mouse clicks to convert to the file format of your preference. Along with all CAD files, I have included all the rendering shown here in 1920x1080 format HD along with the .bip file for keyshot with all the materials already applied, which is a huge timesaver.