Not legal 1 class
Two-stroke internal modification of any kind is prohibited.
IJSBA · Engine
Aftermarket cylinder (2-stroke), IJSBA
IJSBA answers this part for 12 of its classes. 5 of those answers permit the part outright and 4 permit it with stated conditions, leaving 3 that do not.
This page is IJSBA only, and the bodies do not agree. The same part under IHRA. Which one applies to you is decided by whoever sanctions the race you enter.
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.
- 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.
- Legal
- Keep it. The rules permit this part in this class.
Not legal 1 class
No replacement cylinder is listed and no internal modification of any kind is allowed on any engine component, so a two-stroke cylinder may only be bored and have its ports chamfered up to 1.00mm (0.04 in.) at 30 degrees. · RAS.4.1, RAS.4.4
OEM part required 1 class
CYLINDER MUST REMAIN OEM with original port timing. No internal modification of any kind. · VSKL.3.1, VSKL.3.5
Legal, with conditions 1 class
Aftermarket cylinder SLEEVE only, retaining the same port sizes and specifications as OEM, and permitted only where displacement is more than 10% below the 850cc maximum. Cylinder interchange between homologated craft of the same manufacturer is allowed subject to IJSBA restrictions. · SKL.3.12
Legal, with conditions 1 class
Yamaha Waveblaster may upgrade to 701 62T-style cylinders; Yamaha 760 cylinders allowed subject to ignition restrictions; pre-1996 Yamaha may update to 1996+ components. Max 1mm overbore across the board.
- Sport Spec · section headings, no numbered rules
Legal, with conditions 1 class
Machining cylinders for girdle-system heads allowed. · RAL.4.1
Legal, with conditions 1 class
Cylinders may be interchanged between same-manufacturer homologated craft; ports may be added, deleted or reshaped; BUT two-stroke cylinder or crankcase MODIFICATIONS require written IJSBA approval. · SPGP.5.5
Legal 4 classes
The cylinder and cylinder head may be modified or aftermarket.
- Vintage SC · VSC.3.3
- Vintage X2 · VX2.3.3
- Vintage Ski · VSK.3.3
- Freestyle · FREST.3.3
Legal 1 class
Modified or aftermarket cylinder and cylinder head - effectively unrestricted. · SKGP.3.3
Aftermarket cylinder (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.
Engine · two stroke · legal in 9 of 12 answered, 4 with conditions