Air Compressor ??

[Wiseman]

(10-07-2017 )Grizzly Wrote:  However this still doesnt, at least in my mind, explain why I have rev the motor up to 1400 rpm to get it to start filling with air.

This is most likely related to :
1. Bad air compressor governor (really cheap $ )
2. Sticky plunger (controlling the moving valve)inside air compressor head . (Usually caused from soot buildup)

First (and easiest) : engine off
Pull off the 1/4" hose (usually blue color) off air compressor and spray liberally with WD-40. Do the same on the intake of the compressor head too.
Connect it back and start the engine. Let it build air and go off a few times.
Repeat all over again .
If you see improvement , then you'll know air compressor head need replacement .
If no improvement is seen , replace governor .

Be sure your air dryer works properly.