Engine block: Pistons
The pistons are made of light alloy and have grooves for two compression rings and one oil scraper ring.
The upper compression ring is flat and coated with chrome or molybdenum. The lower compression ring has oil scraper properties and is slightly broader than the upper, while the oil-scraper ring itself is in three pieces. The piston in the B235R is tin-coated.
The B235 and B205L/R engines have reinforced pistons with slightly smaller dimensions giving lower compression. Inside, they are adapted to connecting rods with trapezoidal small ends. They also have nitride-hardened gudgeon pins.