How old is the engine and the piston-ring.

Some years ago I bought two small units in OOmodel in china, great service BTW. This units are,

A hall sensor simulator, you just plug the hall sensor connector to this unit, and it fires the plug, you can turn the dial and increase-decrease the firing rate(RPM).
The other unit is similar to those used for checking the timing on full size aircraft engines, it has a LED and buzzer when the hall sensor pass the magnet.

This two tools are very cheap, so cheap shipping was more than the units, so bought units as spares..... I think both are around $7.

Regards