maybe your clutch? or the bell housing has to much pressure on it?? if your talking about that rigged up brake on the clutch. I would of just of took a metal bar like 6 inches made a bracket and hooked it too a foot brake to when you pushed it it pushes the bar on the tire. you see them on a lot...
ya if your not going over 30mph its not to bad even getting sideways because all your weight sets really low tot the ground, and you most of the time you have wide back tires.
yes http://www.affordablegokarts.com/govenor-removal.php i know it may not be your engine but same principle. and the screw with the spring is to richen or lean out your engine. Used for idle and when you take off. like if you take off and it bogs down its either lean or rich not really sure...