tell the difference between .20 & .28
remove the back cover and look at the crankshaft,
.28 is stamped on .28 and .20 is not stamped.
.20 came out first then the .28
The only design change was the remote needle.
The .20 and .28 both have 12 head fins and a
diameter of 1.425"
early .20 had a O-ring for a head gasket but this
was discontinued early in the production. The .20
does not have a head gasket. The .28 uses a head shim.