Hi.

I was a mechanic for a F11 engine in November - RB 25% fuel and RB plug. Before the race it had only been running at idle speed in a bench for 30-40 minutes.
During practice and race we tuned it a little rich (slow 2 stroke). It ran ok under the practise. An ok performace are not enough for us even during break-in , so we changed the plug to a Novarossi C6TGC. Now the engine ran so much smoother even in the cold surroundings (5 -10º Celsius). Still rich HSN.
I don't know if the original plug just went bad after the bench break-in, but for now on he will stick to Novarossi plugs.