If the flywheel does not have any timing marks you can easily find top dead center and the initial injection point:
Trammel the piston. either from the top of the piston or the bottom.
If using the bottom: remove the crankcase door and rotate the crankshaft until the bottom of the piston is parallel to the bottom of the liner. mark the flywheel at the pointer (make a pointer if you need one). Now roll the crank around some more until the piston is again parallel to the bottom of the liner and mark the flywheel at the pointer again.
Measure half way between the two marks, and make a mark at the pointer. Mark half way between the original two marks around the flywheel the other way and make a mark. Now you have both top dead center and bottom dead center. look thru the crankcase door and rotate the crank until the piston is near the top. the mark on the flywheel closest to the pointer is TDC. Mark it TDC.
Measure the circumference of the flywheel and devide that length by 360. (I used milimeters here to make it easier, but you could use inches or cubits) Multiply this by the degrees BTDC for initial injection, and mark the flywheel. Done.
Clear as mud? I had no marks on my Ashwamegh either.
Good luck.