If the engine is turning over slow, the compression reading will be low. The engine must turn over fast, at 300 rpm or better. Have "all" spark plugs removed when checking compression.
S/Plugs still removed, check for spark that should jump a 7/16" gap on all cylinders. Does it? This means that you DO NOT want to test for spark simply by using the spark plug(s) which is a waste of time. If the spark will not jump a 7/16" gap with a strong blue lightning like flame... a real SNAP, then there is an ignition problem. The engine must be turning over at least 300 rpms during this test and have "all" of the spark plugs removed..
What do I mean by a 7/16" gap? The spark plug gap is .030.... you need a tester that you can set to various gaps, 7/16" in this case, to test the spark. No tester? See the following:
Spark Tester - Home Made)(J. Reeves)
A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.
Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:
..........X1..........X2
.................X..(grd)
..........X3..........X4