engine

got an st70 1977 in boxes , to do up like. wrong engine ! .its goin to be a oneoff project so am wanting something with a bit off evrything ...what engines can be fitted with the least hassle?? cheerz merry xmas.

LOTS of engines out there for these bikes.
I'll try to sum up as much as possible:
ST50, ST70, z50, SS50, C50, C70, CF50, CF70, ATC50, CT70, AB02,...
All of these in all there versions so z50j, z50a, st50G, st50E,....
Of course, depending on how P&P you want them to be: 6v or 12v electrics, manual or semi-auto clutch, different wire connectors on ignition,...

HI WAYNUS
Will a C100 50CC engine fit in a st50 frame
Regards Tufty

Tufty,
the C100, C110 and C200 engines should fit pretty easy.
The only 'problem' that can occur is that the mounting bolts trough the frame are somewhat bigger in diameter.
But the location of the mounting holes do line up, unlike the bigger versions (C320,...)
These engines are quite different aside from the 3-gear semi clutch:
- spark plug is located at the left side
- the exhaust pipe connection on the head is smaller
- these engines do not use the distrubution as in ST engines to open/close the valves. The same system as Honda Amigo (PF50), Novio,...

Keep in mind, only a few spare parts, let alone tuning parts, for these engines are available.