110cc - Wierd TDC Issue

[Pitbike Tuner]

Trying to get my engine to top dead center and have the 2 covers off. Issue is when turning counterclockwise and looking thru the top hole for the "t", whenever the engine gets to it it turns quickly past it and I cant get it to hold there. I had the spark plug out as its threads are stripped and I'm going to change the head to fix that issue, but even putting the sparkplug in it does the same.