I use this motor to power a flat bed truck by adding a 35 teeth sprocket to the axel work perfect carry a 300 Lb. on blacktop surface and did well with 200 Lb. on ruff terrain only to find that the chain is slipping quite often.I will like to change the sprocket to a 10T 40 P, I try to remove the nut that holds the sprocket but couldn't get it out.Do any one know what size the shaft is for there is know way to get an accurate measure without taking it a partThanks, hope this help others who is anticipated buying.