Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

The black rubber boot looks better to my thinking, but seemed not to grip the plug as well, leading to  Things moving around, and that secondary spark. While it is true these engines will make enough spark to spark in both the plug gap and outside the engine at the same time, when they do, it makes the resultant firing “soft”, audibly weak and leads to double or triple taps as weak firing fails to speed up the flywheel smartly.
This I learned for certain when I got errant secondary sparks using the brass terminal. So I wrestled the black rubber boot over the terminal and snapped it in place properly. The rubber insulated and stopped the secondary spark.  Immediately what had been a sorta mushy double tap run became a robust single tap With a long coast between taps. For the first time, it sounded like a big hit and miss. Note. I’m running the original governor springs, but they’ve been stretched some.