This is the only big bore kit we've found that bolts on the Eton Sport 50, SYM 50cc and Tomos Nitro 50 without boring out the cases. 72cc displacement.  Most Big Bore kits will not install on this engine unless you bore out the cases. This one will. Does not fit SYM 1P37QMA Motor

Includes Cylinder, Piston, Rings, Wristpin and circlips. 

includes base and head gaskets.

Fits:

Eton Sport 50

Tomos Nitro 50

SYM Symply 50

SYM 50cc Scooters with QMB139 Engine