IJSBA · Exhaust

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

The highest-value 2-stroke performance part and the one with the sharpest class split.

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

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This is one body's answer, not the sport's. You are bound by whichever body sanctions the event you enter. If you race more than one series, build to the stricter answer. The differences are set out in the rulebook comparison.

In Ski Lites and Runabout Stock this part cannot be raced, so a pipe is a choice about which class you enter rather than a part you add to the one you are in.

Where it stands, class by class

12 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

Not legal

This comes off. The rules refuse it in this class.

Legal, with conditions

Keep it, but measure it: the rules permit this part only inside stated limits.

Legal

Keep it. The rules permit this part in this class.

Not legal 1 class

Two-stroke exhaust must remain stock. Stinger insert only. · RAS.4.5

• Runabout Stock

Not legal 1 class

Exhaust must remain stock as supplied by the manufacturer. Only a stinger insert and cooling lines are allowed. · SKL.3.6

• Ski Lites

Legal, with conditions 1 class

Manifold, head pipe and expansion chamber allowed, but exhaust may NOT be relocated and the exit opening may not exceed 2 inches. · VSKL.3.7

• Vintage Ski Limited

Legal, with conditions 1 class

Two-stroke manifold, head pipe, expansion chamber and the chamber-to-waterbox hose may be aftermarket. Exit location and opening size must not change.

• Runabout Naturally Aspirated · RNA

Legal, with conditions 1 class

Kawasaki, Yamaha and Polaris may relocate and replace the chamber. Sea-Doo HX must retain the unmodified stock HX exhaust. Wet-style only; dry pipes and water-jacketed chambers prohibited.

• Sport Spec · section headings, no numbered rules

Legal, with conditions 1 class

Two-stroke chamber allowed; exit may not be relocated, OEM waterbox may not be modified, exit opening may not be oversized. · RAL.4.7

• Runabout Limited

Legal 6 classes

Manifold, head pipe, expansion chamber, waterbox and muffler modified or aftermarket.

• Vintage SC · VSC.3.7
• Vintage X2 · VX2.3.7
• Vintage Ski · VSK.3.7
• Freestyle · FREST.3.7
• Ski Grand Prix · SKGP.3.7
• Sport GP · SPGP.5.9

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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 IJSBA class · where the rulebooks differ · checks on parts the shop sells · how this site reads a rulebook.