RE: Backplate pressure question
I just tried an old .15 Rossi with no muffler and kind of high timing (180 degrees exh.) It wouldn't idle under 10,000 rpm on backplate pressure but went down to about 5 or 6,000 with no pressure on a perry carb. So I would think of it as a cutoff more than a throttle. No check valve or regulator. It started easier on the backplate pressure though.