If you can give me the diameter and tooth count of the gear you have, we can get to a very near perfect pitch estimate. Then again, I am assuming you don't have an accurate measuring tool (calipers/micrometer) since you are asking the shaft size on motor
.
Most 390 sized motors will have 1/8" (
3.175 mm) shafts, but one WLToys pinion gear description says the pinion is 2.3mm. I think that is a typo.
