The cylinder should now be inspected for condition of bore and piston rings. If the bore is worn badly or is scored, it will require re-boring and an oversize piston with rings. The original diameter of the bore is 2.913-in.

Re-boring is generally considered necessary when wear in excess of .008-in. has taken place, or the bore has become damaged or scored.

The rings when new, and when fitted to a new or re-bored cylinder, have gap clearances as follows :-

Compression rings .010-in.

Scraper ring .012-in.

Oversize pistons and rings are made in only two oversizes :-

plus .020-in. (½ mm) and plus .040-in. (1 mm).

No intermediate sizes are used. It is not practicable to fit oversize rings to a worn cylinder, unless the cylinder is re-bored and the appropriate larger piston fitted.

NOTE. If the cylinder is rebored and oversize piston is fitted, the mouth of the combustion chamber will have to be enlarged to clear the top land of the oversize piston.