In 2016 I bought a used Red Wing scale gas engine. Who built it is unknown. It had a set of automobile ignition points for ignition trigger and timing. This, in my opinion, was butt ugly. There was a brass ring with a grove cut in it mounted on the cam gear to open and shut the points. However, poor piston ring sealing made me suspect it had not run much. The brass timing ring on the cam gear prevented the push rod from properly moving back and forth. There was a piece of steel bolted onto the head end of the push rod preventing full stroke return to the cam. The crank and cam gears are plastic and so do not conduct electricity.
I decided to remove this brass ring from the plastic cam gear and make my own timer using a Ford Model T-type buzz coil. The cam was not correctly ground on the low end and I reground it. To modify the cam gear to use the buzz-type coil I drilled through the timing portion of the gear and into the brass bushing. I then tapped the gear and bushing both for 4-40 thread. I used a 4-40 brass screw and J.B. weld to lock it in place. The head of this screw protrudes 1/16 inch and acts as a trigger for the buzz coil. Now I had spark and the exhaust valve opening and closing correctly. I took apart the fuel system and cleaned it. The intake and exhaust valves were good and had correct spring tension. Time to start it up!
I filled the fuel tank, hooked my 12-volt battery to my coil, turned it a few times, actually, many times, and no go. I then hooked it up to an electric motor and let it spin for several hours, hoping the rings would seat. Then I tried to restart it, and finally it did start. It ran about 20 minutes. There was a lot of blow-by and the engine had to hit three to four times to pick up enough speed to latch up. Then there was a rattling noise and the engine stopped. The connecting rod had broken off at the wrist pin.
A few minutes later, a longtime friend called. He races drag cars at Brainerd Raceway, and when I told him what had happened he said I had “put too much nitro methane into the fuel mixture!” When I took the engine apart I found very loose piston rings. I could put a 0.012-inch feeler gauge between the rings and the lands. I decided to re-silver solder the rod to the pin boss and get some wider rings. I ordered new 1-1/4-inch rings, 1/16 inch wider than what was there, and I recut the ring grooves to fit. A look at the wrist pin told me I had to make a new one as the pin retention was just a flat spot on the pin and a 4-40 slotted-head screw. I made a new wrist pin and drilled two holes in it to accept 4-40 hex-head screws, using Loctite to keep it secure.
I had to make a holding jig fixture to correctly align the connecting rod and the wrist pin at a 90-degree angle so I could silver solder them back together. To do this I used a piece of steel 3/4 inch wide, 5/8 inch thick and 8 inches long. At one end I drilled an “N” size hole (0.309 inch) and reamed it to 5/16 inch (0.3125 inch) on the other end. I arc welded a 5/16-inch square nut at 90 degrees to the flat steel. Using a 5/16-inch bolt threaded all the way up to the head as a pusher I was able to solidly hold the rod and pin together for soldering. This would come in handy a second time later on. I silver soldered the small end back onto the connecting rod. Next, I deglazed the cylinder core with 80-grit sandpaper and washed it with soap and water.
I had to make a miniature piston ring compressor to get the pistons and rings back into the cylinder. I decided to break in the new piston rings by using my electric motor setup. After about one hour I started hearing a noise; the rod bearing end of the connecting rod was coming apart so I had to tear it down and start all over. I had to take the connecting rod out, set it up in the rod jig and silver solder the other end. I hoped this was the last of the troubles; another test run would tell.
Another thing I had to do was pin the main bearings so that they would not spin in the journals. I did not want to take the crankshaft out again, so I put locating pins in the main caps. It’s just a brass pin to keep the sleeve bearing from turning and cutting off the lubrication passages for the grease cups. I made a new wood mounting board 9 inches x 16 inches and painted it gloss black. The original skid mount was quite narrow and I was afraid the engine would tip over in transport. The new mount, with rubber pads in the corners, makes for a solid display.
Finally, it was time to start. This time it started fairly easily, and after 15-20 minutes of running settled down, running at 525 rpm. About 80 percent of the time it takes just one hit to maintain speed, otherwise two or three hits, and the blow-by is gone. I think I spent 50 or more hours on this project, and at times it was very frustrating. My friend who races cars looked at my Red Wing engine, noted the 90-degree passages, the spark plug in its tunnel-like hole in the side of the block, the fuel setup and exhaust, and remarked about how inefficient and restricted the design was.