Re: no timing mark
1 does it run smoothly no miss etc
2 put on what you think is top dead center and put a white mark and remove the rocker cover.
now when you move the crank no6 should be rocking (moving up and down) while number 1 doesent move as its on compression.
3inspect hamonic balance for it being spun on the rubber.
it sounds like the harmoic balancer has spun on the rubber and it rooted and needs replacing as its only a matter off time before it spins off completly and goes through your radiator.
Fear leads to arrogance
Arrogance leads to over confidence
Over confidence leads to
remember this young grasshopper