Sounds like a bad spark plug. Although that isn’t much of a test. The resistance across the spark plug gap is much higher under compression. You can cut off the side electrode and use that to check for spark OR use a length of clear flexible plastic with an inside diameter the size of the spark plug wire. In one end goes a shear pin that will go into hde wire contact in the spark plug cap. Wrap the free part with tape so it fits the inside of the plastic tube. There should be enough beyond the rubber spark plug cap to secure with a tie wrap. in the other end of the plastic tube insert a length of spark plug wire with an alligator clip soldered on. Adjust the gap to a quarter inch and secure in place with another tie wrap. That will be your test spark plug. . . 😎
