Troubleshooting a Two-Cycle Engine

The author discusses some of the finer points of adjusting the timing in a two-cycle engine — specifically, early Maytag two-cycle engines.


A collection of Maytag two-cycle engines belonging to Stan Read of Gunnison, Colorado


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Let me continue the discussion I started in the Sep-Oct '67 issue of Gas Engine Magazine on troubleshooting a two-cycle engine.

The little Maytag engines are fairly easy to find and if one does not have too much room for collecting the bigger engines they provide an interesting example of design used on many of the larger two-cycle engines. Most present day two-cycle engines use the reed valve—a thin metal strip covering a machined opening—to allow the fuel-air mix to enter the crankcase and prevent its escape. The vertical Maytag built from 1914-1923 used a brass poppet-type valve to perform this function, and it was located in a small brass carburetor or mixer which also contained a needle valve to regulate the fuel-supply. The later horizontal one-cylinder Maytag used the same type system but more refined in design. The two-cylinder horizontal Maytag used a crankshaft port valve.

Maytag's horizontal engines used the flywheel type magneto similar to most present day small engines. The points are operated by a centrifugal weight type governor which should prevent point operation beyond 1000 to 1050 RPM.

Points should be set to .020 inch on the horizontal Maytag engines, which should properly time them also. If timed properly the points should just begin to open when the piston is one-fourth inch from the top of its stroke outward. Some of the earlier one cylinder models had timing marks on the flywheel which aligned with marks on the plate behind the fly wheel.

Timing is more particular with two-cycle engines than with the four-cycle type since a degree of error at the fly wheel with two cycle operation is a degree of error in ignition, but with four cycle operation represents only a one-half degree of error at the ignition.

Cylinder carbon deposits which raise the compression to the point of ignition can cause poor performance and overheating, which sometimes is mistaken for improper timing. With ignition-governed engines such as Maytag this can also cause "runaway," since ignition becomes independent of the governed electric system. Carbon troubles can be remedied by occasionally cleaning out the combustion chamber and/or leaning the fuel mixture a little at a time until a minimum of smoking occurs at the exhaust. Reducing the oil in the fuel may be required but too much reduction may cause lubrication failure.

I have a 2 or 3 HP hopper cooled, two-cycle Oshkosh engine. (see picture) None of the directories I have list this engine so I do not know where or when it was built or by whom. Do any of you have any information on the Oshkosh? H. C. Doman, Star Foundry & Machine Co., Termaat & Monahan Co., and U. S. Engine Works all built engines at Osh-Kosh, Wisconsin.