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Aftermarket piston assemblies

IJSBA · Engine

Aftermarket piston assemblies

Legal broadly, but the closed-list classes impose geometry and weight constraints.

Where it stands, class by class

20 classes, grouped by the answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules.

Legal, within limits 1 class

Must retain OEM compression ratio, dome profile, skirt length/shape and material type; weight within +/-25.00% of OEM. Non-conforming skirt shapes only with written IJSBA approval.

Legal, within limits 1 class

Within +/-25.00% of OE weight; original port timing, compression ratio, dome profile and skirt retained.

Legal, within limits 1 class

Must also retain original PORT TIMING. +/-25.00% weight.

Legal, within limits 1 class

Must retain original port timing, dome profile, skirt length/shape and material type, and weigh within +/-5.00% of OEM. Note this is 5%, tighter than the 25% used elsewhere.

  • Sport Spec · none - this document uses ALL-CAPS section headings, not numbered rules

Legal, within limits 1 class

+/-25.00% weight, OEM compression/dome/skirt retained.

Legal, within limits 1 class

Non-OEM-replica pistons require written IJSBA approval. · RAL.3.3

Legal 1 class

Aftermarket piston assemblies. · SKSS.3.2

Aftermarket piston assemblies: if the rule your class applies reads differently to you, or the rulebook has changed since this was read, ask. We answer with the section we read it from, or that we have not read it. Ask a rules question.

Every IJSBA class · where the rulebooks differ · signed checks on parts the shop sells.

Engine · two and four stroke · legal outright in 20 of 20

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