Crankcase Method
In this method the crankcase doors are opened up and the piston is visually checked whether is going up or down. This is the surest method, but a bit cumbersome. It should be used when you have a strong doubt about the other methods.
Valve Spring Method
This is not an independent method but is used in conjunction with the flywheel method. In this method if the flywheel is indicating two units, you can check the springs of both the units. The unit in which the springs are loose is the one at TDC. The caution is that this method is useful for an engine in use. If you have removed the rocker arms during the overhaul and thereafter you want to use this method then it can cause errors.
