TOHATSU MFS 25D Service Manual page 198

Power Unit
23) Inspection of Cylinder Head
1. Remove the carbon build-up of the combustion chamber,
and check for deterioration, corrosion of mating surfaces,
etc.
Use a straight edge 1 and thickness gauge 2 to check
2.
the distortion of the cylinder head in the directions shown
in the diagram. Replace if greater than the specified value.
Cylinder Head Distortion Limit:
0.1 mm (0.004 in)
5-58 4st 25/30 2022