Glad we can help - hopefully it is help. The C-75/85 engine was supplied with a Stromberg carburetor. It has a mixture control on the top of the carburetor, which is often wired full rich. As it is thought that leaning is not required below 5000 feet msl. The assembly can be carefully removed without taking the carburetter off and cleaned if rough idleing occurs. It is composed of a small disc with three holes in it to adjust the air fuel mixture. If you ioperate in dusty conditions, the holes sometimes get clogged.
I installed a cable on mine to see the effect of leaning, and could not notice any difference in the 5 -7000 ft altitude I fly, so I removed it and safetied it full rich again. One more thing not to go wrong... The Continental Maintence and Overhaul manual, on page 29, states : "7-9 Stopping the engine. Allow the engine to cool by running it at approximately 1000 RPM for a few minutes; then stop by turning the ignition switch to the "OFF" position. If a Stromberg Carburetter is installed, open the throttle wide during the last few revolutions. If a Marvel-Schebler carburetor is installed, leave the throttle closed." My note : the Stromberg does not have an acceleration pump, the Marvel- Schebler does. Without an acceleration pump, if you open the throttle suddenly, the engine will sputter as it goes lean. I suspect the reason they direct you to open the throlttle fully as the prop slows down is to prevent "run-on" that could be caused by hot carbon deposits in the cylinder head. Opening the throttle as the prop slows down introduces cool air, extinguishing and hot spots. Additional note: Because the carburetor and manifold contains a fuel air mixture, you need - do I need to say this - to be extra careful in turning the prop. If the ignition switch grounding is bad, the engine may start ! You should always assume that an engine is ready to start - so be careful around all aircraft propellers. No question is too simple or stupid. Only the un-asked are. Pleased we can help. Regards, Harry Francis 93530 BCB
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