Bike engine . Want to add two similar bike engine on a single shaft (https://i.stack.imgur.com/qMN5u.jpg)
closed as too broad by raydowe, Rory Alsop, MooseLucifer, Chenmunka, anonymous2 Aug 23 '17 at 11:31
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I found this article pretty quickly. It's an entire project about exactly that - how to run 2 IC engines together. There's way too much information for me to even decide what to quote, but it's all about the subject of running 2 engines.