Aftermarket or lightened flywheel, IHRA

IHRA answers this part for 29 of its classes. 4 of those answers permit the part outright and 0 permit it with stated conditions, leaving 25 that do not. 4 of the ones that do not are classes we read as open rather than as refusing it. 24 are inferred from how the class is written rather than quoted from a rule naming this part.

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

Where it stands, class by class

29 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

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: 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.

OEM part required 1 class

OEM stock and unmodified. Sea-Doo HX must retain the OEM 720 flywheel. · U.4.1

Sport Spec

Not permitted, not listed in the rules 20 classes

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

Legal 3 classes

The flywheel and flywheel cover may be modified or aftermarket, as may the ignition system and electrical box, and the battery charging circuit may be disabled or removed entirely.

Ski GP · K.6.2, K.6.3
Sport GP · V.7.2, V.7.3
Runabout GP · X.5.2

Legal 1 class

On these two-strokes the flywheel is the magneto rotor that powers and triggers the ignition, so it is read as part of the ignition system that S.4.2 lets be modified or replaced with aftermarket parts, total loss ignition included. S.4.3 adds aftermarket or modified flywheel covers. · S.4.2, S.4.3

Ski Vintage

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.

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

Aftermarket or lightened flywheel: 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 IHRA class · where the rulebooks differ · checks on parts the shop sells · how this site reads a rulebook.

Ignition · two and four stroke · legal in 4 of 29 answered