Caille updated their racer in 1928 as the model 30.
This Caille Model 30 also was a badge motor made for Sears and Roebuck and sold by them as a Motorgo. The only difference between the Caille and Motorgo versions were decals.
The serial number, which is stamped on the cap on the flywheel begins with SR and this is the "tell" for Motorgo. Caille used the letter "M" as a prefix at times with the same meaning.
The Model 30 is one of the easiest Cailles to identify because of the auxillary air intakes on the front of the motor on either side of the carb. They were used for increased speed.
Model 30s were shipped with a tractor prop, as well as the usual 3 bladed prop, which turned a fishing motor into a racer of sorts.
The Model 30 was the last Caille to carry the air shutter extra air inlets. The carb was set pretty rich to make starting easy and was small-ish to allow reasonable low rpm operation. Once you were warmed up and going you could open 2 little extra air shutters on the intake manifold to let in more air and go faster. This probably worked better than a larger carb would have worked given the 1920's carb technology.
