If your engine has suddenly become a bad starter its unlikely to be fuel timing.
However to time the engine you need to look on the rim of the flywheel for the timing marks (as your engine is a three cylinder, there will be three zig zag lines), these need to be lined up on the pointer on the engine (this can be found on the fltwheel end of the fuel pump rocker arm box).
The spill timing on these engines is 20 degrees BTDC, or 3.45" from TDC (on a 19.3/4" dia flywheel).