I have a friend who bought a Stinger 40cc twin and is quite impressed with the quality of the Stinger engines but mentioned that the threads in the plug hole never matched the overall quality of the engine and that the plugs were quite loose while being screwed into the cylinder head. Sure hope that you find a way in solving your plug problem.
I was very interested in getting one of the Stinger 20cc SE exhaust engines but have been turned of by the use of the very fragile 1/4-32 plug. Hopefully sometime soon RCGF will see to making a change to using the pretty common and very sturdy CM-6 plug.
Last edited by karolh; 05-07-2021 at 10:24 AM.