What should the rpm's reading be when I am using a APC 12x10 at full throttle.

I have one of these old girls....it's been eons!

Are you on a pipe? What fuel?

12-10 ought to give you 10-11K if memory serves. Bear in mind this engine was not designed to turn a billion RPM....it was designed to do useful work at a modest rpm.... (it's quieter that way)

Great engine by the way....A Rolls Royce amongst Yugos.

'Nite