Supercharged Side-Valve Harley-Davidson

Paul is a motorsport fabricator who does a lot of custom one-offs for people—they have ideas that can’t be bought so he helps them achieve it—so everywhere you look at Paul’s Harley, it’s one custom one-off part after another.

I GOT the engine, gearbox and supercharger from a friend of mine, Bill Mcnamara. I’d helped him build a supercharger set-up for a WLA he intended to ride around Australia; he ended up not using the supercharger and I ended up with it.

The motor was 90 percent new-old-stock in waxed paper. Johno Johnson, who used to be Redfern Motor Cycle Spares, rebuilt the motor as a favour for Bill. It’s a 1940 ‘W’ motor, not a WLA. Apparently there were only 53 made.

I built a jig to hold the engine and gearbox sitting the way I wanted it, then I built a frame around the outside. I had already helped build the supercharger for another side-valve Harley so I knew exactly how it was all going to go; and all I did was make enough room in the back chain stays, height wise, to make it fit.

Bill had the gear around the outside of the clutch to drive the supercharger machined up by a guy in Mona Vale (Sydney’s Northern Beaches).

There’s no battery. The motor runs off a Hunt magneto; and it’s got an original generator with a Cycle Electric Alternator Conversion kit and a 14 volt capacitor to run the lights (once the capacitor gets to 14 volts, it controls the charging from the alternator).

The primary drive was an oil drip feed but I blocked the drip off and I just put chain lube on both the chain drives.

Originally, when I made the manifold for the supercharger, it was for a S&S butterfly carb but it was too hard to tune in; very difficult to ride; and then Bill put the SU carb on it and it actually worked a lot better. I was thinking the original carb was too big a diameter; the SU is quite a bit smaller. It can be a bit piggish cold, but once it warms up, it goes real nice.

I came up with the idea for that front-end and a mate, Ben Shore, and I sat and drew it in 3D CAD and he machined it on his mill. We spent 20 hours drawing and it took about four hours to machine.

The front wheel is from a Honda CRF 450 motocross. I chose it because it was a narrow hub set-up and I wanted keep it all fairly narrow.

The handlebars are stock CB 250, and I machined up a couple of threaded bungs for risers and welded them to the handlebars.

The headlight is half of a street-fighter headlight unit. A customer bought me his bike and I took that set-up off and put another on for him; he said you can have it and I held one up and said that’s alright; made a couple of brackets and that was it.

I found the fuel tank on eBay. It’s from an Italian moped from the 1960’s. I just modified the tunnel to fit. I made up an aluminium oil tank for the side of the bike. The seat was an eBay buy.

The back guard was from an American guy called Seven Metal West who hand-rolls them; then I made a sissy-bar to hold it up. The tail-light is a neat little solid-brass LED unit.

Kyle Smith at Smiths Concepts painted the bike form me.

The single leg frame is made from a good grade steel, it’s not rubbish, but it’s not very rigid so I’m currently building a twin-leg frame from chrome-moly with a slightly different look.

The furthest ride I’ve done so far is from Sydney to Bathurst return. I did it over two days.

If I had to describe this bike, I’d say it’s half-way between a bobber and a chopper…

words by Paul Mckinnon; photos by George

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