Seems you don't know how to precisely locate the T.D.C.
To do this you need a timing wheel with fixation screw, an indicaton pointer made from steel wire or sheet metal, an a "piston stop tool". See this DIY video
https://www.youtube.com/watch?v=xAwRulNylGs.
Finding T.D.C.:
- attach the timing wheel to your crankshaft (use LH side M8 thread which appears behind the hex plug in the primary cover)
- cut/bend an appropriate pointer and fix it to the engine, so it shows you the actual angle of the crankshaft when properly aligned with the timing wheel's dial
- screw the piston stop into the spark plug's thread and lock the counter nut
- adjust the stop's spindle so that the crankshaft can be rotated for roughly 6-7/8 of a turn.
- either stopping point has exactly the same angular distance to T.D.C. !
- take the stop out
- turn the crankshaft to an angle halfways between the two stopping points measured before
- now your piston is precisely in T.D.C. position
Hans