I just maidened my DP Extra with a BME 50 inverted, BME muffler (loud), on 87 octane with Lawn Boy ashless at 40:1. I have 2 questions.

1) The engine sets up pefectly on the groung but the low /mid goes very rich in the air. Someone mentioned that I have to put a fitting on the diaphragm fitting on the carb as the ram air effect is changing the setting. The cowl is open in front and the prop blast is right on the hole.

2) I am getting a black, oily residue out of the exhaust. It is thick, nasty stuff. Definitely not metal to meatal type stuff. Am I using the right oil/mixture for breakin? Is this just a byproduct of the rich condition? Is it harmful to my engine? Engine has tons of power with a Menz 20x10s and runs well. Just starts to burble rich in the air at lower throttle settings. Any help will be appreciated. TIA, cbk