I need a new clone engine for my 1965 Honda s65 motorcycle. Which will fit?

I need a new clone engine for my 1965 Honda s65 motorcycle. Which will fit? - 1

I would try a bigger engine. The motor mounts look about right. The S65 was my first motorcycle! Notice the second source uses a lifan 125 cc motor, maybe you can contact him and ask if he had any problems installing it.

See http://www.ebay.com/...1713651414
http://www.ebay.com/...1845114887

How about rebuilding what you have? Its EASY.

I'm ok with mechanical but not very familiar with engines. Is there a engine-for-idiot book?