Power on speedo by holding for three seconds and it will go into calibration mode. Hold full throttle, press button. Hold full brake, press button again. ESC will power cycle and you should be good to go.
Where exactly in this procedure are you having the "pull full throttle and nothing happens" problem? The motor will not receive power during calibration, if that is what you are referring to?
Also, make sure your throttle and brake are at 100% when doing the above. I had an issue at carpet nats that Mark (Smyka) had to help me with where I had my throttle set to 100 (I had forgotten that max is 150 on KO) and the speedo wouldn't calibrate. Seemed like it wouldn't find neutral correctly.
If you also ever have an issue where your speedo won't turn off when you hold down the button, you should recalibrate the speedo to your radio and it should fix the problem.