Inspecting Cylinders

Special Tools:

P 13c Cylinder gauge setting ring

Standard Size

(Note: 1 mm = 0,03937 in)

 Group  Cylinder Diameter  Piston Diameter
  -1  82,485 - 82,494  82,47
  0  82,495 - 82,504  82,48
  +1  82,505 - 82,514  82,49

1st Oversize

 Group  Cylinder Diameter  Piston Diameter
  -1 KD 1  82,985 - 82,994  82,97
  0 KD 1  82,995 - 83,004  82,98
  +1 KD 1  83,005 - 83,014  82,99

The above tables show which piston and cylinder size groups can be paired.

Wear limit is a clearance of 0,2 mm ( 0.008 in) between piston and cylinder. Exact piston to cylinder clearance can be determined only by measuring each component separately.

Measure cylinders at a point approximately 15 mm (3/4 in) below the cylinder top using a bore micrometer with setting ring P 13c.

Replace cylinders which are worn close to the permissible wear limit.
912_fig_128 All cylinders are marked at the base to indicate the bore diameter group, such as "0", or reconditioned units by "+ 1 KD I" etc.

The piston tops bear appropriate size values (+1 KD 1, etc),

The piston to cylinder clearance when new is 0.02 mm (0.0008 in), the wear limit is 0.2 mm (0.008 in).

Cylinders worn close to the wear limit should be replaced together with pistons; use cylinder / piston replacement sets falling into the appropriate size group. Piston/ cylinder sets installed in one engine may not differ by more than four size groups.


The Biral cylinders are available in four height groups; cylinder height is the distance between the cylinder seating flanges at the crankcase and the cylinder head.

Cylinders installed under one cylinder head must be of same height and bear same identifying symbols at the cylinder base. The identifying symbol is a triangle inside which the number 5, 6, 7, or 8 is stamped, depending on the particular size group.
Last modified: Mon, 17 Jan 2005


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