Tinkering up the Old M-20/35


| September/October 1975



Engine owned by the Oakland Telephone Co

Howard E. Shideler

35640 Avenue F, Yucaipa, California 92399

When I was a young lad during those golden days on the farm, a group of some 20 farmers went in on shares and purchased a Case 20-40 two-cylindered opposed type gas tractor and a companion 28-50 separator. These fine agricultural instruments were delivered by our good Mr. Jack Kadinger who now resides near Sioux Falls, South Dakota. In the era of open-type drive gearing, I still believe that was one of the very best tractors that was ever built. A very was building fine two and four-cylindered opposed engines, but hamstrung themselves with about the most ridiculous (sliding frame) transmission that one could possible conceive of. -All to save one intermediate gear; which idea was wrong to begin with since a pair of spur gears can be properly cut only to mesh between themselves. The root becomes dislodged if one of a pair of such gears is brought into an improper mesh with another gear of differing pitch diameter than that of the paired original design. One of my brother-in-laws nearly met disaster when descending a good grade with an Avery 40-80 and the frame slid forward out of mesh. And were they bugaboos to handle in the belt!

At that time, one of the most popular other tractors of that rating was the Oil Pull. In the large models (as in the Case 30-60 also) the engines had a 360-degree two-throw crankshaft, which allowed of a more smooth power flow and also a straight longitudinal vibration. However, in the smaller sizes the Rumely builders for some reason went to the 1800-degree crankshaft. The carburetion advantages were the same, as a short downdraft was achieved for both cylinders; but this design entailed a severe cross-vibration such that many owners experienced trouble with the Tim-ken bearings in the front wheels through not keeping them properly adjusted. So, when I became afflicted with the engine bug again some 14 years ago, I considered myself fortunate in finding an old M-20-35 Oil Pull in the junk yard in Spokane, Washington. This specimen I immediately bargained for, and now it sits in my back yard and is called upon now and then to perform some little task. Immediately after finding this old girl, I ran across a sister engine in the junk yard in Pullman, Washington. The latter engine was equipped with angle grouters, which I would have preferred to the spade lugs on the wheels and extensions of my cherished possession. On my little old lady, someone had removed the magneto, put several wrinkles in her fenders, discarded the foot brake and other small items, and, apparently- what had caused her near demise- her former owner must never have looked to the lubricating oil in the separately enclosed governor housing. For I was to discover that not only was this reservoir plumb long since dried up, but the lack of oil had caused the governor shaft to seize and become twisted off. Doubtless some farmer must have had a fast final ride before getting her shut off, and it is somewhat of a wonder that things did not begin flying to pieces.

My first chore after getting the old M delivered to my home at that time in Tacoma, was to rig up an automobile distributor (grinding off all but the two necessary cams) and get her into operation, with battery ignition. Then it was steam cleaning and finally painting, until she 'shone like new.' Then a friend gave me an old Edison-Splitdorf magneto, and I was able to dispense with the battery for a few months until the mag went real sick in its old age. After trying a few other mags, and moving the engine to my present home, I secured an American Bosch four-terminal magneto ; upon which I fixed two spark gaps on the extra terminals, and so far this seems to be doing nicely.

Oh yes, the water tank had long since rusted away, I suppose. And since kerosene or distillate was difficult to obtain, and the engine would not be placed back into full agricultural service anyway, it became of advantage to simply operate on straight gasoline. Actually, the gasoline of today is probably inferior to the kerosene of yesteryear. Of course, there is the problem of detonation and more rapid burning without water, but if one can tolerate the slight diminishment in output power, a good remedy is to set the spark back to about ten degrees BTC. This puts it into the class of other tractors which were built to operate on gasoline, like the old Case mentioned earlier. And since this model does not have the crankcase vent back into the intake system, there can never be any fear from intake backfires. I can vouch that the power output is still adequate, since an instance of hauling long green eucalyptus logs up out of a ditch nearby, the old girl could spin her rear wheels right into the ground if tied down to a standstill.

Now this latter piece of work posed another problem, and if the fool-killer had not been taking his day off I can assure you that I might not now be writing this article. You see, I was backing up to the very edge of a 30-foot embankment of some 60 degrees standing, and tying onto those trees of about 25 feet in length and 24 inches in diameter, with 40 feet of log chain. Well, after hauling in the last of a dozen such very heavy green fellows, I proceeded to put the old girl back under the canopy. And I just made it, for upon the last clutch disengagement, the throw out yoke slid over the worn sleeve engagement! Had this happened while attempting to stop in reverse at the very edge of the embankment, likely the whole works of us would have had the fastest ride ever in her life down that embankment. So we come to the crux of this story and one which elicited a few new swear words from my capacious vocabulary. No matter how good the mechanic, he had always best consult the owner's manual before attempting to make repairs on such design of clutch. But no manual was available, and only through the medium of this fine magazine did I find a great help in the kindly assistance and Xeroxing of some manual pages from such book in the possession of a greatly esteemed friend, Mr. Donald Robbins of Troy, Ohio, who has one of the Super Oil Pulls at work in a sawmill operation. And because this is pretty heavy work without good shop equipment for such undertaking, I put off the job long as I could.