Piston rings for POLINI 210/221 - selection according to cylinder material and piston type
At POLINI, the ring configuration is not only a question of diameter, but above all of cylinder material. This is why - despite identical piston dimensions - there are different piston ringsfor aluminum cylinders (coated raceway) and cast iron cylinders (cast iron raceway).
Which rings do I need?
For aluminum cy linders: Rings with coating on the track side - designed for coated cylinder tracks (e.g. Nikasil).
For gray cast iron cylinders: Rings without this coating - suitable for classic gray cast iron tracks.
Compatibility rule (short and clear)
OK: Coated aluminum cylinder rings can be used in grey cast iron cylinders.
Not recommended: Uncoated cast iron rings in aluminum cylinders (lack of raceway coating on ring side).
Ø and cylinder generation (important for older cast iron cylinders)
Ø 68.5 mm: suitable for Polini 210/221 (piston/cylinder designed for 68.5 mm).
Old cast iron 207cc cylinders: Ø 68.0 mm ex works (before 2023). Drilling/honing is required for 68.5 mm pistons/rings.
Cast iron oversize: Ø 68.8 mm only use after overhaul (drilling and honing).
TIP for ring assembly
Piston rings are sensitive: do not overstretch when expanding. With keystone rings, it is essential to ensure the correct installation position (only one direction fits). If a ring does not move freely: carefully loosen, turn and reinsert.
Note: Always consider the cylinder material (aluminum/cast iron), actual bore and desired running clearance to find the right combination. If in doubt, measure the cylinder dimensions and then select the tolerance class or ring type.
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