Ring saw engine, part 2

[John in MA]

What I've found after partially tearing it down has changed my thought of "what were they thinking" to "what were they smoking."

All the housing parts are obviously made by a completely different company from whoever made the powerhead. In fact, the engine is entirely self-contained with only standard-looking bolt holes for the housing parts to attach to. The only OEM ID I've managed to find is a sheetmetal tag on the crankcase that says "T-1554" and a "D" with wings cast into the block. Now the physical description:

The cylinder and crankcase are one piece, with a separate cylinder head. Several flat spots are cast into the cylinder, presumably for possible decomp valve installations. There is also a metal plate at the rear of the crankcase. It's where the reed plate and carb would go on an old outboard, but this is just a cover. The exhaust ports are three round holes under the muffler. The intake port system is where this thing gets crazy: The carb attaches to a plastic manifold on one side of the cylinder. Seems normal enough, right? Well, under the manifold are four round intake ports arranged in a square. Two of them are uncovered at the top of the stroke, two are uncovered at the bottom. The manifold only feeds to the first set. There's also a rectangular port going into the crankcase! I know I haven't seen as many small engines as most of the guys on this site, but I have never, ever seen a saw, outboard, or other tool with an engine like this.

Does anyone know what the hell I'm dealing with? It's really fun taking it apart: everything removed reveals more surprises.

Yes, photos will be taken before it goes back together.

 

[Walt Galer]

Howdy John,

Yep, it sounds like an outboard all right. In fact, I would suspect a loop scanvenged engine by Johnson about 1972 to 1974! Someone must have had a real brainstorm. You may have a "windowed" piston skirt in there, by the way, with the windows on the side opposite of the exhaust port.

The very large transfer ports is why they had to have the cylinder as part of the crankcase casting, as is done in outboards.

The idea was to use the incomming charge to drive the exhaust gasses out the exhaust port.

Regards,
Walt Galer

 

[John in MA]

Did they make a general purpose engine? I can't see this being an OMC product for an outboard. They didn't have any single cylinder, air cooled outboards of this size at the time. They had a little 1.x HP single, but the next step up was a 3HP water cooled twin. This also doesn't have a windowed skirt and the piston face is absolutely flat.

I thought either Tecumseh or Clinton outboard when I first saw this thing, but I don't think it's one now.

I've found more in the meantime. Displacement is approx. 78cc's. There are two more transfer ports the other side from the two I found. The way they're done is very interesting. It looks like holes were drilled from the inside of the crankcase and more through the side of the cylinder. The cylinder holes were then plugged from the outside. And finally, this thing has a ferrous pressed-in cylinder liner.

 

[Walt Galer]

Howdy John,

I did not mean it was an outboard, just that type of design converted to an aircooled general purpose engine. It's news to me who actually made your baby! Without the windowed piston skirt, it must be some rather unigue design. It could have been something someone like Techcumseh tried, and gave up on. Let us know when you solve it.

Regards,
Walt Galer