Pistons

Pistons

General Data

Mean Piston Velocity at 5000 rpm* 13 m/s
*applies to both B204 and B235R engines

Piston Types





Classification of Pistons and Cylinder Bores

The piston classification is stamped on the piston crown roof. Piston classifications for service are:

AB

B

C

The cylinder classification is stamped on the cylinder face and is specified for each cylinder. The cylinder classifications are:

A

B

B+

They can all occur in the same cylinder block.

Piston Classification

Standard A (not a spare part)
B204 89.971-89.980 mm
B235R 89.966-89.975 mm

Standard AB
B204 89.980-89.989 mm
B235R no specification given

Standard B
B204 89.989-90.000 mm
B235R 89.975-89.984 mm

Standard C
B204 90.000-90.013 mm
B235R no specification given

First Oversize (0.5)
B204 90.472-90.488 mm
B235R 90.475-90.484 mm

Second Oversize (1.0)
B204 90.972-90.988 mm
B235R 90.975-90.984 mm

Piston Clearance, Nominal
B204 0.011-0.040 mm
B235R 0.025-0.044 mm

Classification, Piston/Cylinder

A/A
B204 0.020-0.041 mm
B235R 0.031-0.069 mm

AB/A
B204 0.011-0.032 mm
B235R no specification given

AB/B
B204 0.014-0.040 mm
B235R no specification given

B/B
B204 0.006-0.031 mm
B235R 0.031-0.069 mm

B/B+
B204 0.011-0.041 mm
B235R no specification given

Piston Diameter

Piston diameter is measured at right angles to the gudgeon pin hole, 9.3 mm (B204L) or 11 mm (B204i) from the bottom edge of the piston.