Diagram showing distortion of the piston movement

Content Tools

559 Sheldon Road, Palmyra, New York 14522

Well, here it is November the 21st and the shows are over for another year. And another wet one it was! At the Pageant of. Steam at Canandaigua, N.Y. we were nearly rained out, but it wasn't quite as bad as it was in 1976. At the Western New York Gas & Steam Engine Show at Alexander, N.Y. the mud was hub deep and the show was finally canceled. Let's hope 1978 will treat us with good weather at show times.

At nearly all the shows that I have been to, a too common sight is an engine belching smoke and running way too hot. If an engine is properly timed and the water hopper is free of any foreign material and not belted to anything, it should run at about 160 degrees. It's understandable that if an engine has new rings it will run hotter than normal. Lubrication of the piston is important. With the trip raised on the oiler, adjust the top screw so that it will drop from 15 to 20 drops per minute-depending on the size of engine and load. While piston should always be kept well lubricated, too much oil will coat the piston and cylinder head, which will burn as engine gets hot, and cause premature ignition. Too much will also throw blue smoke out of the exhaust. Not enough oil will cause a dry, coughing noise at the open end of the cylinder and later out the piston. It will also make the engine heat up very quickly.

Diagram showing distortion of the piston movement due to angularity of the connecting rod. For clearness of diagram the piston is not shown as its movement is the same as that of the wrist pin.

In the diagram accompanying this article, I have shown the distortion of the piston movement due to the angularity of the connecting rod. It relates to the various angles the connecting rod makes with the cylinder axis during the stroke. Starting at the beginning of the down stroke, the angularity of the rod causes the piston to move more than half of its stroke while the crank is moving the first 90 degrees or quarter of its revolution. The reverse conditions obtain during the return stroke.

It must be understood then that the power delivered from the explosive charge ignited just prior to top dead center is derived from the first degrees of travel of the crank and the piston more or less goes along for the ride for the next 90 degrees.

Make sure your engine is timed right. On most engines the timing mark on the small gear on the crankshaft has a punch mark that should mesh with two punch marks on the large cam gear. On International Tom Thumb and Famous engines there is no timing mark on the small gear. The timing mark is on the end of the pin that holds the small gear on the crankshaft. I might mention here, if you have been looking for the serial number on a Tom Thumb or Famous engine you will find it on the end of the crankshaft on the crank end. When the two gears are properly meshed the exhaust valve start to open very near the end of the power stroke and should remain open until the crank is about 10 degrees before the exhaust stroke is finished. Adjustment can be made by turning the bolt on the rocker arm in or out whichever is needed. Ignition of the fuel should occur at about 10 degrees before top dead center. Actually the fuel is not fully ignited until the piston is at top dead center. If you spilled some gasoline on the ground in a line of about three or four feet and lit one end of it, you will notice it takes a fraction of a second to reach the other end. The same principle pertain to the gasoline in the cylinder. And remember when timing an engine with make and break, ignition takes place when the points break away, not when they make contact.

On most Briggs-Strattons, the timing cannot be changed. On some of the older models like the models 9, 14, 19, 23 and 23A the timing can be changed. On engines like the Cunningham, Reo, Tecumseh and others timing can also be changed. Timing on these small engines is usually set at 10 or 11 degrees before top dead center.

Ever wonder what the speed of your engine is? First it should never be greater than its rating, which can be ascertained by counting the revolutions of the large gear and doubling the count. Or count the revolutions of the flywheel key.

An easier way is to hold your hand on the exhaust lever and count how many times per minute it hits the large cam. Multiply this number by four, and you have the speed of your engine.

For collectors who have Maytags, this information will be helpful to you. On all single cylinder models, the point and plugs are both set at .020'. On twin cylinders, set the points at .020', and the plugs at .037'. When testing the spark on either plug, always ground the other plug wire. An easier way to start a twin is to ground one plug wire between the plug and the cylinder head, then after engine is started put the plug wire back on the plug. When mixing your oil and gasoline, use 1 part oil to 16 parts gasoline. If you have just put in new rings, it would be wise to use a little more oil in your mixture. I use Quaker State Outboard Motor Oil with good results. Your Maytag will smoke less with this type of mixture.

If you have an engine with make break and need an induction coil, why not make your own. It's really quite simple. I use a soft steel rod, about 5? inches long. First I put the rod in a lath and turn one end of it down to about ? or 3/8 variable speed drill. Next get 100 feet of 18 gauge copper coated wire. Make sure your steel rod is ? inch. Put your drill in your vice, next insert the turned down portion of the Steel rod in the chuck, then wind on the 100 feet of wire. And there you have an induction coil that will work better than a factory job. It will work on either 6 or 12 volt batteries.