1. "F" Timing Mark - indicates top of the piston travel (Top Dead Center).
2. "T" Timing Mark - indicates ignition timing (when using the stock plug with a 0.024 - 0.028in gap).
These marks are visible by removing the flywheel housing cover.
Camshaft Timing Marks (50 and 70cc Engine)
1. "X" Timing Mark - indicates the camshaft timing.
This mark is visible by removing the valve cover.