IJSBA · Engine

Aftermarket cylinder head (2-stroke), IJSBA

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

This page is IJSBA only, and the bodies do not agree. The same part under IHRA and UIM. Which one applies to you is decided by whoever sanctions the race you enter.

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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. If you race more than one series, build to the stricter answer. The differences are set out in the rulebook comparison.

Where it stands, class by class

12 classes, grouped where the same rule gives the same answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules.

What each answer below means

Not permitted, not listed in the rules

Treat it as coming off. The class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list, so this is our reading rather than a rule we can quote at you.

Legal, with conditions

Keep it, but measure it: the rules permit this part only inside stated limits.

Legal

Keep it. The rules permit this part in this class.

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 · SKL

Legal, with conditions 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 · section headings, no numbered rules

Legal 5 classes

The cylinder and cylinder head may be modified or aftermarket.

• Vintage SC · VSC.3.3
• Vintage X2 · VX2.3.3
• Vintage Ski · VSK.3.3
• Freestyle · FREST.3.3
• Ski Grand Prix · SKGP.3.3

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

The two-stroke cylinder head may be modified or aftermarket. · SPGP.5.7

• Sport GP

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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 · checks on parts the shop sells · how this site reads a rulebook.