If it's a twin cylinder remove one spark plug, Rotate the engine by hand until you feel it getting harder to rotate. This is the beginning of compression stroke (piston is on the way up to TDC), Then remove the remaining plug and stick a small screwdriver into the plug hole.
Rotate slowly until the piston pushes the screwdriver up out of the hole, Once you hit TDC the screwdriver will start going back down. That's known as after TDC......
Originally Posted by piston slapper
You never learn anything until you admit you don't know it all...
"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!