Not permitted, not listed in the rules 4 classes
On a closed list an unlisted modification is not permitted. · A.2.2, J.1
IHRA · Fuel
IHRA answers this part for 15 of its classes. 5 of those answers permit the part outright and 1 permit it with stated conditions, leaving 9 that do not. 4 of the ones that do not are classes we read as open rather than as refusing it. 9 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 UIM. Which one applies to you is decided by whoever sanctions the race you enter.
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.
Not permitted, not listed in the rules 4 classes
On a closed list an unlisted modification is not permitted. · A.2.2, J.1
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
Legal, with conditions 1 class
Reed petals may be modified or aftermarket. The reed cage assembly must remain OE. · O.3.3
Legal 2 classes
The reed valve assembly may be modified or aftermarket, with no limit stated on petals, cage or spacers.
Legal 1 class
Reed valve assemblies may be modified or aftermarket and reed spacers may be added. · U.3.2
Legal 1 class
Two-stroke entries: Full assemblies, broader than Ski Lites O.3.3. · P.2.3
Legal 1 class
Two-stroke entries: Aftermarket permitted. · BB.5.6
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.
Aftermarket reed valve assembly: 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.
Fuel · two stroke · legal in 6 of 15 answered, 1 with conditions