Sportman, I used the original plug until last Sat. It finally went. If you are using 10% to 15% nitro I would use a no.8 glow plug.
If you are using low or no nitro you would need to use a hot glow plug. I am running a lower nitro fuel so I am using a hotter glow plug. I strickly use the type "F" plug on my four strokes. No idle bars!