I couldn’t find a 9 tooth sprocket for bicycle chain that would fit the MY1016 motor so I had to make a sprocket from scratch. If you find you need to do this there are some pretty good videos on the web that explain the process better than I can. But here are the basics. Sprocket teeth are spaced evenly around a circle and the size of that circle is determined by the number of teeth you want, the pitch of chain you are using and the size of pin that holds the chain links together. The formula PD=P/(sin[180/N] will get you started.
PD = Pitch Diameter
P = Pitch
N = Number of Teeth
PD or Pitch Diameter is an imaginary circle through which the center of each chain pin travels as it rotates around the sprocket. Once we know the Pitch Diameter we divide that number in half to get the radius of the Pitch Circle. We can then draw that circle on paper or on a steel plate. Using a compass, scribe or other marking tool we can then mark every chain pin center all around the circle using the chains pitch (the distance between any two chain pin centers) as our distance. Once those chain pin centers have all been marked they can be drilled using a drill diameter equal to the chain pin diameter. The peripheral material is removed and the basic sprocket remains.
For example, I wanted a 9 tooth sprocket that would drive a bicycle chain. Thus, my “N” was 9 and my “P” was .5, which is the pitch of almost all bicycle chains. Using the formula for Pitch Diameter my result was 1.4619”. So using half that amount as my radius a circle was drawn on steel plate (in my case I used an old and ruined power saw blade). I then used a compass set at .5 inch to mark the pin centers around the circle. (Photo 1) I then drilled each hole with an 8mm (or 5/16) bit to match the pin size of the chain links. (Photo 2) The outer material is carefully removed using an angle grinder with a cutting blade and then with a file. (Photo 3 and 4)
The MY1016 motor uses a “D” type drive shaft with one side of the shaft cut flat. (Photo 5). To match the flatted shaft and prevent the sprocket from slipping when under power, a small triangle is cut from 1/8” steel plate and attached to the sprocket with a dab of JB Weld. (Photo 6) This holds the small tab in the correct position until it can be mig welded in place. A steel washer is cut to complete the circle around the drive shaft. (Photo 7). The sprocket assembly is removed from the motor and the triangular tab and the washer are welded to the sprocket and ground as smooth as you can get it. (Photo 8) Mine is not real pretty but it works.