This madman can’t stop adding cylinders to motorcycle engines

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Allen Millyard

A proper engine rebuild requires patience, tools, and a heap of expertise. What Allen Millyard does, extensively modifying motorcycle engines, requires all of that plus a certain mixture of talent and insanity. His latest video, posted on YouTube, is a reminder that he operates at a different level than most home mechanics.

Millyard re-engineers factory motorcycle engines, often adding to their cylinder count. He’s best known for turning vintage Kawasaki Z1 four-cylinders into six-cylinders, but his madness is not limited to one brand or machine.

Over the years, Millyard has also built a few custom Honda engines. The engines highlighted in this latest video are versions from the Honda SS50, a bike that uses a single horizontal cylinder and displaces 50 cc from the factory. Millyard had to tear one down recently, so we got a fascinating look into how he added a duplicate 50-cc vertical cylinder to make a V-twin. The whole project is incredible impressive, and there aren’t even many factory gaskets for Millyard to use because he machined away so much of the aluminum engine case.

The final product has factory-like fit and finish, and the bike looks like an absolute blast to ride. While he doesn’t mention a specific figure for power output, I can only imagine it’s capable of more than what most 100-cc engines make. The lightweight and compact packaging would surely make for lively character on what most Americans would call a “starter bike,” and the high-rpm power on the finished machine would be seriously addicting. I’ve got a lot of respect for anyone who so casually can describe and explain the intricate and complicated processes necessary to build a custom engine of this nature.


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