Briggs 3HP horizontal shaft with Pulsa-Jet/Fixed Jet carburetor adjustment
Greetings Folks,
I am working on a 3HP Briggs and Stratton horizontal shaft motor, #80232-2242-01. It has a Pulsa-Jet/Fixed-Jet carburetor on it. I thoroughly cleaned the carburetor and replaced the diaphragm on it and installed with new intake and gas tank gaskets. The motor starts and pretty well with no stumble, etc.
The Pulsa-Jet/Fixed-Jet carburetor has only a single "idle mixture valve (screw)", no outer brass bolt or internal jet like on some other B&S carburetor styles. I followed the manual steps for final adjustment by warming the motor up and, starting from 1-1/2 turns out, I turned the idle mixture screw clockwise until lightly seated which resulted in no change of RPM, nor indications the mixture was leaning out. Basically, no significant change of how the motor runs when turning screw clockwise or counterclockwise. The service manual indicates a recommended idle speed of 1750 rpm, I am getting about 2000 RPMs with the throttle valve adjustment screw set adjusted out to nearly its lowest setting.
The idle mixture screw isn't damaged, tip is good and no marks suggesting overly tightened. I went ahead an ordered a new OEM idle mixture screw and spring anyway.
I would appreciate any thoughts/ideas of what else I should be looking at. There is a small welch plug above the idle mixture screw and I am contemplating pulling and replacing it (I'm not sure what is behind the small welch plug as diagrams don't show that).
Thank in advance for any advice,
PBM