This thread sounds exactly like the problems I'm having. I don't have a tack but I'm sure I'm no where close to 12,000 RPM. I'm running a 14x6 prop on a Goldberg Ultimate using 10% fuel. I've had the engine for about seven years, but it doesn't have a lot of time on it. I loved the engine when it was working good but it's been a real headache lately. I think I need a rebuild too.

Where is a good place to send it?