have had very good luck with Fox plugs. I always have an assortment of them in my flight box. If they are bad contact Fox. They may be able or willing to replace them. The standard long with idle bars work very well for me in all of my engines. I use the miracle plugs in my Saito 4 strokers. Tey work as well as the factory plugs. I hope you get this soerted out. Let us know how you make out.

Mark Shuman