IJSBA · Engine

Aftermarket cylinder head (2-stroke)

Vintage Ski Limited is the notable case: cylinder OEM, head free.

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This is one body's answer, not the sport's. You are bound by whichever body sanctions the event you enter, and where both govern you, you are held to the stricter of the two. The differences are set out in the rulebook comparison.

Where it stands, class by class

12 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.

Not permitted, not listed in the rules Our reading, not a rule we can quote at you. This class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list.

Not permitted, not listed in the rules 1 class

Not listed in this class document. Illegal under the closed-list principle.

• Runabout Stock · RAS

Not permitted, not listed in the rules 1 class

No aftermarket head allowance in · SKL

• Ski Lites

Legal, within limits 1 class

Compression capped: Kawasaki and Yamaha max 190 psi with min 0.040 in squish; Sea-Doo HX max 175 psi with min 0.051 in squish. Drop-down style domes prohibited on all models.

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

Legal 4 classes

Explicitly permitted by this class document.

• Vintage SC · VSC
• Vintage X2 · VX2
• Vintage Ski · VSK
• Freestyle · FREST

Legal 2 classes

Two-stroke cylinder head and gasket aftermarket.

• Runabout Naturally Aspirated · RNA
• Runabout Limited · RAL

Legal 1 class

The cylinder HEAD may be modified or aftermarket even though the cylinder may not. · VSKL.3.6

• Vintage Ski Limited

Legal 1 class

SKGP.3.3

• Ski Grand Prix · SKGP

Legal 1 class

SPGP.5.7

• Sport GP · SPGP

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Aftermarket cylinder head (2-stroke): 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.