Restoring a Simplicity Engine

Simplicity engine before restoration

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9025 Phoebe Ct. Annandale, Virginia 22003

The engine was complete when I got it, but in pretty sad shape after having sat outdoors for over twenty years. We thoroughly rebuilt it over a span of several months, with Mac doing the necessary machine work. This included making a new tappet roller and pin for the pushrod, and also a new piston pin bushing and honing it to fit the original pin. He bushed the rocker arm and pushrod clevis, and made a new shaft for the governor detent arm and bushed the arm itself. The cylinder cleaned up okay, and the bearings were in excellent shape; they appear to have been repoured sometime during the engine's working life. In restoring the engine, the two most difficult jobs were presented by the camshaft bore, and strangely, the cam itself. On this engine, the camshaft turns in a hole bored directly through the side of the block, with no bushing. The shaft was in good shape, but the hole was badly worn. The tough part was setting the block up to accurately bore the hole oversize for a bushing, without changing the centerline of the hole. Mac came up with a good way to do it, which I will describe here; perhaps it will help somebody with a similar problem.

First, he set the block on a horizontal milling machine and clamped it to the table. Next, he placed a piece of precision round stock through the main bearing bores, and mounted a dial indicator on the milling machine's over arm. He took X and Y direction readings at the outside of each main bearing bore and shifted the engine block on the table until it was square with the over arm and spindle centerlines, then tightened the clamps and rechecked readings. Then he moved the machine table to bring the camshaft bore visually into line with the spindle centerline. He installed a dial test indicator in the boring head and took two X and two Y readings on the camshaft bore; then shifted the table as necessary to bring the camshaft centerline into the spindle centerline. He bored the hole until all taper and out-of-round was removed, then added enough diameter to provide for the chosen bushing wall thickness. He machined the new bushing from Concast 660 bearing bronze, installed it, and honed it to fit the shaft.

The problem with the cam itself had to do with the igniter lobe. When we took the engine apart, we noticed that the igniter lobe had been built up with babbitt. We couldn't figure out why until we assembled the engine. No matter how we adjusted every thing, the igniter would not trip at the correct time. Evidently the lobe had broken or worn off, and someone tried to replace it with babbitt. Unfortunately, they put the lobe in the wrong location by several degrees, and the engine couldn't possibly have run. Perhaps this was why it was retired. Mac decided on a correct cam profile, and after melting off the old babbitt lobe built a new one using a silicon-aluminum-bronze alloy rod. We spent the next few hours shaping the new lobe to fire exactly right-a long and tiresome process.

The igniter needed some attention. I built up the worn shaft, then turned it back to size and fitted it, and made a new return spring. The points looked okay, although I later replaced them and the mica washers. Mac ground the valve seats, and we assembled the engine with new valves, valve guide inserts, and piston rings. I sandblasted and cleaned the engine while it was apart, and painted it in stages during assembly. The color scheme is correct, based upon traces of the original paint found on both the engine and the skids. The colors are Dupont Dulux #24166 (Brewster Green) and Red Devil acrylic latex enamel (Crimson). The Simplicity name on the hopper is yellow. When I built the new oak skids, I used the original skids for patterns, so they are also authentic. I should note that Mac and I run all our engines on propane gas. Since I wanted the Simplicity to look completely original, I had to devise a way to hide the gas regulator and fuel hose. I did this by extending the carburetor fuel pickup tube through the bottom of the gasoline tank. The small propane hose attaches to the tube under the gasoline tank, and runs through the bottom of the battery box to the regulator hidden inside. The supply hose from the propane tank also enters the bottom of the battery box, at the front.

With the fuel system worked out, the engine was finally ready to go. Unfortunately, this didn't turn out to be one of those 'it started on the first crank' stories. In fact, it took a lot of cranking before we got the bugs worked out and the mixture just right. Later, the engine began burning up the igniter points even though I had a condensor in the system. I replaced the points, and the old Simplicity has run fine ever since. I've seen a few other Simplicity engines, but nobody I talked to knew much about them. I understand that the Turner Mfg. Co. stopped building Simplicity engines about 1918-1920. Mine is serial #AB1497, and I estimate it was built in the early to mid teens, based on the other engines I've seen. If anyone could share more information on Simplicity engines with me, I'd really appreciate hearing from them.