Full porting service (ports reshaped, runners modified), IJSBA

A service rather than a part, but legal or not by class exactly like one.

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

Where it stands, class by class

20 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 6 classes

Only the 1.00mm / 30-degree chamfer. Abrasive port cleaning is prohibited.

Fixed Steering Ski Stock · FSSK.3.1
Runabout Rec Lites · RRL.3.1
Ski Stock · SSK
Four Stroke Ski Lites · FSKL.3.1
Runabout Naturally Aspirated · RNA.3.1, RNA.4.1, RNA.4.4
Runabout Stock · RAS.3.1, RAS.4.1, RAS.4.4

Not legal 1 class

Original port timing must be retained. Chamfer only.

Vintage Ski Limited · VSKL

Not legal 1 class

Port chamfering is capped at 1.00mm (0.04 in.) at 30 degrees and no internal modification of any engine component is allowed. The cylinder clause also says any cylinder modification needs written IJSBA approval, and the document does not say how that sits with the ban. · SKL.3.1, SKL.3.5, SKL.3.12

Ski Lites

Not legal 1 class

Cylinder port modification beyond the 1.00mm / 30-degree chamfer is prohibited.

Sport Spec · section headings, no numbered rules

Not legal 1 class

The SKM document gives no chamfering allowance at all. Internal grinding, machining and polishing prohibited.

Ski Modified · SKM

Not legal 1 class

Chamfer only. · RAL.3.1

Runabout Limited

Legal, with conditions 1 class

Two-stroke cylinder modifications require WRITTEN IJSBA APPROVAL. · SPGP.5.5

Sport GP

Legal 3 classes

Intake and exhaust ports may be modified; diameters and shapes may be changed.

Vintage SC · VSC.3.2, VSC.3.3
Vintage X2 · VX2.3.2, VX2.3.3
Vintage Ski · VSK.3.2

Legal 2 classes

Intake and exhaust ports may be modified in diameter and shape, runners modified or built up, combustion chambers modified.

Ski Superstock · SKSS.3.2
Runabout Open / GP · ROP.4.2

Legal 2 classes

Two-stroke cylinders may be modified or aftermarket, and four-stroke intake and exhaust ports may be changed in diameter and shape with runners and combustion chambers modified.

Freestyle · FREST.3.3, FREST.7.2
Ski Grand Prix · SKGP.3.3, SKGP.6.2, SKGP.7.2

Legal 1 class

Full porting legal. · RSS.3.3

Runabout Superstock

Full porting service (ports reshaped, runners modified): 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 and four stroke · legal in 9 of 20 answered, 1 with conditions