A 5 hp Piersen and Good Intentions

By Staff

Last issue, I noted my ongoing motions toward finally getting my 1920 5 hp Piersen running. With the engine finally pulled out and occupying the middle of my shop, I was confident that I’d finally make some real headway on it – to the point I suggested I might even have it running by now. Heck, I was so sure of myself, I even plugged it in the table of contents as an upcoming, next issue article, confident my good intentions would be met with success. Well, we all know the old saw about good intentions and the road to hell …

But it’s not all bad, because I did in fact make some progress with the Piersen. With the engine finally cleaned up a bit, it was quick work to confirm a good hot spark from the non-stock Wico Model X/XH150B magneto. From what I can find, the original magneto should have been a Berling, a Dixie or an Ohmer, although it appears the latter was used after Piersen was acquired by Collis in Clinton, Iowa, around 1921.

It won’t fire successive revolutions, but I have gotten it to bark a dozen-plus times. Funny enough, at the same time I was working on the Piersen, managing editor Landon Hall was working on his scruffy, new-to-him 1974 Norton 850 Commando motorcycle. Totally by luck, both engines fired for the first time in who knows how long at exactly the same moment!

With a good spark confirmed, I turned my attention to the mixer, which is an over-flow design. The incoming air charge passes through a gulp valve of sorts, a spring-loaded disc that appears to open against spring pressure during intake in response to cylinder vacuum. The fuel charge is pulled in with the incoming air, passing through a simple jet at the base of the mixer. I suspect the mixer works, but so far I’ve been using the priming cup for starting and I haven’t been able to spin the engine fast enough or long enough to get successive combustion cycles. Unlike an engine with a spoked flywheel, there’s little to grab to really get the engine spinning, and there’s presently no hand crank, which, as we know, is something of a twin-edged sword.

A potential issue is what appears to be an unpredictable loss of compression, as if one of the valves is hanging up. When compression is present, it’s surprisingly fierce, requiring a fair bit of effort to spin the flywheel. But occasionally, it’s as if the engine has latched out, and it spins easily. A bit more inspection should confirm the issue.

The old oil’s been drainedand replaced (I’m always amazed how clean non-detergent oil looks even after untold years of sitting) and I’ve confirmed the Piersen’s odd oil reservoir – a Ball canning jar – works properly. Next up is a thorough cleaning of the gas tank and, I hope, finally getting it to bark for more than one or two revolutions.

Richard Backus

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