+ 1 on PDW's post above.
The straight line next to the "T lying on its side," indicates TDC when aligned with the slot at the bottom of the "timing hole." Since the flywheel/rotor is anchored to the crankshaft rotation with a Woodruff key, this indication is absolute and intact, unless the Woodruff key is sheared/missing. The cam chain/sprocket alignment has nothing to do with TDC (although valve (camshaft) timing and valve clearance must be set at TDC between compression and power strokes, when all valves are completely closed and camshaft lobes point away from the center of the engine).
There are TWO piston TDC positions each four-stroke cycle; you want the one mentioned for examination/adjustment.
The "F" mark is used to monitor ignition timing. At idle, the straight line next to the F is illuminated by a timing light at the center of the slot at the bottom of the timing hole; as rpm increases, the F mark and the line "move" clockwise. The F mark line appears before the T lying on its side line as the engine is rotated counter-clockwise when viewed from the engine left side.
Last edited by Damocles; 04-02-2017 at 02:18 AM.