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Class Legality

UIM · Exhaust

Aftermarket expansion chamber / tuned pipe (2-stroke), UIM

The sharpest class split in the UIM book, and it mirrors IJSBA almost exactly.

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

Ski GP3 is the UIM analogue of IJSBA Ski Lites: the 800cc two-stroke stand-up class, and no aftermarket pipe is legal in it. Scrutineering is a late place to find that out.

Where it stands, class by class

19 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. 5 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.
Legal, with conditions
Keep it, but measure it: the rules permit this part only inside stated limits.
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.

OEM part required 3 classes

The exhaust system must remain entirely of origin as delivered by the manufacturer, so the original expansion chamber is required under 501.02.03.03. · 501.02.03.03

OEM part required 1 class

The exhaust system must remain entirely of origin as delivered by the manufacturer, so the original expansion chamber is required under 502.02.03-03. · 502.02.03-03

Legal, with conditions 1 class

Manifold, head pipe, expansion chamber and connecting hose aftermarket; OEM waterbox mandatory; exit opening size and position maintained. · 502.03.03-07

Legal, with conditions 1 class

Manifold, head pipe, expansion chamber, gaskets and the chamber-to-waterbox hose may be modified or aftermarket. The OEM WATERBOX must be used unmodified, the exit opening size and position must be maintained, and no tuned portion may protrude outside the hull. · 501.03.03.07

No rule, this is an open class 3 classes

No exhaust article beyond the turbo water-cooling rule. Free under the open-list reading.

No rule, this is an open class 2 classes

No exhaust article at all, so the same open-list reading applies here as in Ski GP1.

Aftermarket expansion chamber / tuned pipe (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 UIM class · where the rulebooks differ · checks on parts the shop sells · how this site reads a rulebook.

Exhaust · two stroke · legal in 2 of 11 answered, all with conditions

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BaddJet Class Legality