This is undeniably one of the most dangerous, and potentially fun, project motorcycles we have ever featured on the pages of Silodrome.
It’s a highly modified Honda Monkey Bike that is now powered by an inline-four cylinder engine from a Honda CB350F, in place of the tiny 49cc single-cylinder engine it would have been fitted with originally.
Fast Facts – A 350cc Honda Monkey Bike
- This Honda Monkey Bike is likely one of the fastest minibikes ever built, or at least it would be if it was ready to ride.
- It’s powered by an air-cooled 350cc inline-four cylinder engine from a Honda CB350F which produces 34 bhp at 10,000 rpm, with a top speed of 100 mph.
- The Honda CB350F was the smallest capacity four cylinder motorcycle ever put into mass production when it entered the market in 1972. It was built until 1974 and replaced by the CB400F in 1975.
- The Monkey Bike you see here is being sold with minimal additional information, it clearly has a highly modified frame to accommodate the engine, but it’s unfinished and will require some work to get running and rideable.
A Pocket-Sized Widowmaker
Project motorcycles come in all shapes and sizes, the one golden rule is that you should (generally speaking) never buy someone else’s unfinished project bike, as they’re typically a Pandora’s Box of unfinished work, missing parts, and bodged jobs.
That said, sometimes an unfinished project bike comes along that’s just too interesting to ignore, like the wild 350cc Honda Monkey Bike shown here.
Honda originally unveiled their Monkey Bike series, designated “Z50”, in 1967. The entire project to build these pint-sized motorcycles had been started almost by accident.
Honda had developed some minibikes for kids to use at a carnival in Japan, it turned out that the adults loved riding them too, but when adults rode them they looked like monkeys with their knees and elbows out. This resulted in them being nicknamed “monkey bikes” and the name stuck.
The Z50 series of minibikes were typically fitted with 49cc, air-cooled single-cylinder engines of unit construction with built-in transmissions. Early bikes had no suspension at all, except for the tire sidewalls of course, but later models received telescopic forks, and later still twin rear shock absorbers were introduced.
The pocket-sized widowmaker project bike listed here uses much of the original Monkey Bike frame, though its been significantly modified to accommodate the new, much larger CB350F engine.
This bike has some limited front suspension but none on the rear, and there’s no sign of a front brake either, just a drum brake the size of a dime.
The original four carburetor set up has been replaced with an easier to tune twin carb arrangement. The seat needs to be properly fitted, both the rear brake and clutch cables need to be attached properly, that rear sprocket needs to be replaced with something more suitably sized, and there are doubtless many other small jobs that need to be done.
If you’d like to read more about this unusual bike or register to bid you can click here to visit the listing on Mecum. It’s due to roll across the auction block in late January.
Images courtesy of Mecum
Ben has had his work featured on CNN, Popular Mechanics, Smithsonian Magazine, Road & Track Magazine, the official Pinterest blog, the official eBay Motors blog, BuzzFeed, and many more.
Silodrome was founded by Ben back in 2010, in the years since the site has grown to become a world leader in the alternative and vintage motoring sector, with millions of readers around the world and many hundreds of thousands of followers on social media.