FRUSTRATIONS and Fond Memories


| September/October 1995



Nelson Brothers Jumbo engine

P.O. Box 78 Summit Station, Pennsylvania 17979

I guess everyone who has been collecting engines for a while eventually makes a buy that they have second thoughts about. In early 1994 I attended an engine consignment auction, looking for a project to keep me busy. There was a large selection of engines to choose from, but I got to the auction later than I had planned and didn't have time to look them over as thoroughly as I like to. When a two horse Nelson Brothers Jumbo came up for bid. I was pleased to get it for a reasonable price. I had looked over the engine beforehand and knew it had a split head and some other problems, but I didn't notice the cracked and poorly repaired flywheel until I was loading it onto my truck. The thrill that usually accompanies a new acquisition was dampened somewhat by this discovery, as well as the concern that the crankshaft might not run true, since it was mushroomed on the end with the bad flywheel.

When I got the engine home I stored it in the garage for a few months, until I finished a two horse Fairbanks-Morse I was working on. By April I was ready to tackle the Jumbo. Gauging the crank showed it ran true, despite the damage on the end. When I pulled the flywheel, it was apparent it was a total loss. My spirits raised somewhat when I was able to pick up a replacement flywheel from Hit & Miss Enterprises.

I trued the crank-end by belting the Jumbo to another engine and working it back into shape with a file and emery cloth. Next, I pulled the head and took it to the welding shop to have the cracks repaired. After having the head welded, I filed the weld back to the original profile of the head and then filled a few weld pits with a metal epoxy. After priming, it was impossible to detect the repair. I then ground the valves on the lathe and lapped the seats with grinding compound.

The side rod was the next headache, because the original had been replaced with a poorly fabricated one that was bent and cracked. I turned a new one on the lathe, out of steel bar stock, and after drilling and tapping the necessary holes had a rod as good as new. The rocker arm shaft was also missing and had been replaced with a bolt. Another evening's work at the lathe yielded a suitable shaft as near to the original as I could make it. Additionally, I had to make a new magneto trip rod, a new pin for the governor assembly, a spark advance lever, a gas cap, and speed adjustment screw. Parts to repair included the choke, the needle valves, and an assortment of shims and bushings to take the play out of a host of worn parts.

After cleaning all the castings I painted and started the reassembly process. I prefer to leave bolts, springs, and all the running parts free of paint. Instead of paint I clean them on a wire wheel then blue them with gun bluing. A coat of wax or boiled linseed oil helps to further protect them from rust.