As supplied, the FS-70S2, FS-91S2 and FS-91S2-P have their
throttle lever on the right hand side and needle-valve control on
the left. However, where more convenient for certain installations,
these positions may be reversed after rotating the carburettor
through 180° horizontally.
Proceed as follows.
RELOCATION OF CARBURETTOR CONTROLS
Remove the intake pipe mounting screws from the cylinder head
(taking care not to lose the flange gasket [91S2/91S2-P] ) and
the carburettor mounting screws from the crankcase cover plate
bracket.
Detach short tube connecting carburettor to pump unit (FS-91S
2-P) and gently rotate the carburettor through 180° without
separating it from the intake pipe or removing the enclosed Oring
seal.
Re-install the complete sub-assembly of intake pipe and
carburettor, making sure that adjoining surfaces are clean.
Tighten screws evenly and firmly but not excessively.
Remove pump mounting screws from the crankcase cover
plate lugs, carefully rotate the pump clockwise one-quarter turn
and attach it to the second pair of lugs provided, taking care that
the central tube connecting the crank chamber to the pump
diaphragm chamber is not twisted.
Finally, make sure that all external tube connections are secure
and do not leak. As per OS web site. Hope this helps.