If you are looking at the two speed you will see the outside gear has what appears to be an aluminum hub in the center of the gear, this is actually a clutch that engages second gear as the gear RPM increases. Now look at the outside gear and you will notice it has a lip that the aluminum clutch sits inside of. Spin the gear slowly and locate the hole in that lip. Once you have located the hole in the lip you can spin the aluminum clutch slowly until you see a small screw through the hole in the lip. That is your adjustment screw, tightening it should bring the 2nd gear shift higher and loosening should lower it. DO NOT OVER TIGHTEN THE SCREW, what your actually adjusting is spring tension on the clutch, if you over tighten the screw you will damage the spring assembly. I will see about making a video if this does not make any sense.