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Class Legality

UIM · Engine

Aftermarket head gasket, UIM

UIM answers this part for 16 of its classes, and publishes no rule for it in 8 more. 2 of those answers permit the part outright and 4 permit it with stated conditions, leaving 10 that do not. 5 of the ones that do not are classes we read as open rather than as refusing it. 7 are inferred from how the class is written rather than quoted from a rule naming this part. 8 are inherited from a parent class the rulebook points at.

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

Base gasket thickness is a hard number a tech inspector can measure: 0.8 mm in GP3, 1.52 mm in GP2. Publish the thickness on the listing.

Where it stands, class by class

24 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. 8 of them borrow another class’s rules and are marked below; for those, the link to the parent class is read from the categories table rather than stated in the rulebook. 8 publish no rule for this part and name no parent to borrow one from, and are grouped together at the end.

What each answer below means

OEM part required
This comes off. Only the part the manufacturer fitted is allowed here.
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.
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.
No rule published for this class
Unanswerable here. This class publishes no rule for the part and names no parent class to borrow one from, which is an absence in the rulebook and not a permission.

Not permitted, not listed in the rules 2 classes

Not listed in this class. Illegal under the class's own stock clause.

Legal, with conditions 1 class

Base gasket not thicker than 0.8 mm. · 502.02.03-06

Legal 2 classes

Two-stroke cylinder head AND GASKET may be modified or aftermarket.

Aftermarket head gasket: 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 UIM class · where the rulebooks differ · checks on parts the shop sells · how this site reads a rulebook.

Engine · two and four stroke · legal in 6 of 16 answered, 4 with conditions

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BaddJet Class Legality