A Piezo Crystal Furnishes the Ignition

February/March 1997
Paul F. Brien 
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4312 Lone Oak Road Nashville, Tennessee 37215

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A friend of mine gave me this air compressor to convert into a hit and miss engine, an offer I couldn't refuse. It turned out to be NOS, as the hone marks were still evident on the wall of the 17/8 dia. x 1 stroke cylinder. The crankshaft runs in Timken taper roller bearings. I had to weld an extension on the back end of the crankshaft to support the second flywheel, and upon checking the hole in the front cover, I noticed it was around .003 larger all around than the crankshaft passing through it. Then I realized the purpose of that reed type valve on the top of the crankcase: On the down stroke of the piston, air is compressed in the crankcase and this is vented out through the flapper valve, while the vacuum formed inside there, on the upstroke, sucks any oil trying to get out around the crankshaft back into the crankcase. So I machined the same clearance around the new shaft end in the back cover. This works very well, as I have experienced no oil leakage in this area at all.

I really liked the cylinder head on this compressor with its fins and the two valve locations just right to position my valves inside the cylinder area. It was simple to ream out the air valves and press in cast iron guides for the valve stems. These were NOS Lauson engine valves. On an air compressor the piston, of course, comes almost smack up against the head, so I inserted between the head and the cylinder a ? thick cast iron spacer bored out around 7/16 deep to form a combustion chamber that would give me about a 4 :1 compression ratio. As the valve seats are in this insert and the valve guides are in the head, I doweled them together with 3/16 pins to maintain alignment. I used 'O' rings to seal both joints, as it looked like there was not much area here for a regular head gasket to hold.

The timing gears are Briggs &. Stratton, as is the mixer valve and also the flyweight governor, which was internal on some model B&S. I had to add some steel pins for added weight to the flyweights to have enough 'umph' to slide the tapered spool back to operate the push rod latch-out properly. The two rough flywheel castings were purchased from Tiny Power Models. I made the gas tank from a piece of 2' brass pipe I had and the ends are from ? brass sheet soft soldered in with 95/5 solder. The ends are bumped out just to give the tank a little 'character.'

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