You have the 66/80, (66cc), Flying Horse motor, hence the pic of the winged horse Pegasus and the FH-80 on your connecting rod
It is a motor I really would not pour any more money into.
Bikeberry markets or used to market the Flying Horse as a low end, entry level motor but I have not seen one that was a one piece cylinder, the few I have seen in person has a separate head on them.
In my personal opinion, it is one of the original throw away motors in this little hobby/sport of ours, better to put money aside and get a new motor for yourself that you will get alot more out of as regards take off torque power, more rapid acceleration, higher top end, etc, etc, etc.