IHRA · Engine

Base gasket thickness change, IHRA

IHRA answers this part for 15 of its classes. 0 of those answers permit the part outright and 3 permit it with stated conditions, leaving 12 that do not. 4 of the ones that do not are classes we read as open rather than as refusing it. 12 are inferred from how the class is written rather than quoted from a rule naming this part.

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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

15 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.

No rule, this is an open class

Probably keep it. The class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms, and this is our reading rather than a permission anybody wrote down.

Not permitted, not listed in the rules 7 classes

On a closed list an unlisted modification is not permitted. · A.2.2, J.1

• Runabout GP2
• Runabout GP3
• Sport Spec
• Runabout Limited
• X2 Vintage
• Ski Vintage
• Sport GP

Not permitted, not listed in the rules 1 class

DD.7 states no engine type, so a two-stroke entry cannot be ruled out, and DD.7 does not list this part, so under the DD preamble it is not legal on either engine. · DD.7

• Drag, Turbo No Nitrous

Legal, with conditions 1 class

Limits: max thickness 0.8 mm, sub 780cc min thickness 0.5 mm. · O.2.6

• Ski Lites

Legal, with conditions 1 class

Limits: two stroke max thickness 0.8 mm. · M.2.1

• Ski GP3

Legal, with conditions 1 class

P.2.2 opens only the head gasket, so a two-stroke base gasket stays within O.2.6, at no more than 0.8 mm thick, with 0.5 mm allowed on an engine under 780 cc. · O.2.6, P.2.2

• Ski Limited

No rule, this is an open class 3 classes

The class states only what it bans and calls itself run what you brung, against a section DD preamble that says anything unlisted is illegal.

• Drag, 2 Stroke Unlimited · DD.12
• Drag, Stand Up Unlimited · DD.10
• Drag, Unlimited · DD.6

No rule, this is an open class 1 class

No restriction in section CC, and CC.1 permits any modification it does not restrict.

• Freestyle · CC

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Base gasket thickness change: 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.

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