Not permitted, not listed in the rules 3 classes
On a closed list an unlisted modification is not permitted. · A.2.2, J.1
IHRA · Engine
Aftermarket cylinder head (2-stroke)
IHRA answers this part for 14 of its classes. 7 of those answers are permissions, with or without limits attached, and 7 are not. 7 are inferred from how the class is written rather than quoted from a rule naming this part.
Where it stands, class by class
14 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.
Legal, within limits 1 class
On the Kawasaki X2 pre-2005, the X2 2005 to 2007 and the Yamaha WaveBlaster 701 drop-down domes are prohibited, with maximum compression 190 lb and minimum squish clearance 0.04 in. On the Sea-Doo HX drop-down domes are prohibited, with maximum compression 175 lb and minimum squish clearance 0.051 in. · U.2.4
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
Aftermarket permitted.
- X2 Vintage · T.2.6
- Ski Vintage · S.2.7
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
Aftermarket cylinder head (2-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 · two stroke · legal outright in 7 of 14