saw a pic of a modified Hummer bicycle with a Zenoah BE30 2-stroke engine.
Neat installation, which retain the gear shift, guessed it climbs well, as well as having a decent top speed, since it integrates with the gear system on the bicycle, which is the challenge for most friction drive.
see link:
http://www.motorfans.com.cn/bbs/viewthread.php?tid=16979095&page=1&sid=NP4Q8U#pid19410162
Neat installation, which retain the gear shift, guessed it climbs well, as well as having a decent top speed, since it integrates with the gear system on the bicycle, which is the challenge for most friction drive.
see link:
http://www.motorfans.com.cn/bbs/viewthread.php?tid=16979095&page=1&sid=NP4Q8U#pid19410162