Re: 1939 Champion S1E and D1E 1 cylinder motors.

[hotrod]

According to the parts book and a service bulletin, only the D1E had synchronized controls in ’39. All models after ’39 had it.
A Champion with serial number 5523 should be a 1936 model 1B. A model A carb is stamped MS-85A. Only the model ‘A’ rope sheave is flat on top and its flywheel nut is visible. You could remove your steering mounting arm and compare the serial number stamped into your crankcase there, with the number stamped into the front of the motor to see if they match.
Champion offered underwater exhaust as an option for 1937-1939 models that didn’t have it. (I don’t know if they offered it for the ’35-’36 models.)