Advice needed please. On my Prince i can select 1st Gear ok. When you go for second with the pedal at full travel it doesn't quite go in all the way but if you let the pedal return then put gentle pressure on it you can feel the indent plunger locate. This is the same for 3rd and 4th but top will drop out if you put the power on to much, come out of gear every couple of miles or so. Which adjustment is required please. Not much good at following Richardson's instructions in the book.