Super 8 50 has the same 139 engine as the agility, so the restrictions are the same (in most areas) The drive boss is #22105, and has a shoulder on it . You can buy a new boss for about $30.00 or machine off the collar.. You MAY have a plug in the air box right in front of the carb that limits the air flow .It is a square block w/ a 1" hole in it. If you have that you also have the smaller main jet .068 I believe. Those can be removed, and an .085 main installed. Those mods will get you to 45mph.