OEM part required 3 classes
Must remain OEM. No porting.
- Drag, Yamaha Pro Stock · DD.1
- Drag, Sea-Doo Pro Stock · DD.2
- Drag, Yamaha Spec · DD.3
IHRA · Engine
Cylinder head work (4-stroke)
IHRA answers this part for 24 of its classes. 7 of those answers are permissions, with or without limits attached, and 17 are not. 12 are inferred from how the class is written rather than quoted from a rule naming this part.
Where it stands, class by class
24 classes, grouped by the 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 Our reading, not a rule we can quote at you. This class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list.
No rule, this is an open class Our reading, not a rule we can quote at you. This class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms.
OEM part required 1 class
Original casting required for 1101cc+. Valve count must not change. · K.2.6
OEM part required 1 class
Original casting matching the engine block must be used. · X.2.6
Not permitted, not listed in the rules 9 classes
On a closed list an unlisted modification is not permitted. · A.2.2, J.1
Legal, within limits 1 class
Bead blast chambers only with valves seated. Ports must NOT be bead blasted or abrasively cleaned. · W.2.2
Legal, within limits 1 class
On the Kawasaki 750SX, 750SXI, 750SXI Pro and SXR800 drop-down domes are not allowed and O-ring head sealing with no head gasket is permitted, with a minimum dome of 28cc. · M.6.1.1
Legal, within limits 1 class
Model-dependent. Two-stroke entries: Aftermarket permitted. V.2.7 Four-stroke entries: Original casting required; runners, chamber, valve placement modifiable. · V.4.8
Legal 2 classes
Two-stroke entries: Aftermarket permitted.
- Ski Limited · P.2.2
- Runabout Limited · BB.3.5
Legal 2 classes
Porting allowed.
- Drag, Sea-Doo Spec · DD.4
- Drag, Super Stock · DD.5
No rule, this is an open class 2 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, 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
Cylinder head work (4-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 IHRA class · where the rulebooks differ · signed checks on parts the shop sells.
Engine · four stroke · legal outright in 7 of 24