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Class Legality

IHRA · ski

Ski Vintage

IHRA 2026, S. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

  • 1Not legal
  • 1OEM part required
  • 15Not permitted, not listed in the rules
  • 26Legal, with conditions
  • 18Legal

Read out of the published IHRA rulebook on 2026-09-11, so confirm anything that decides a purchase. The full note is at the foot of the page.

Running the class

Eligible craft
The Kawasaki 550 is the primary eligible craft. A Vintage 650 or Vintage 701 class may be offered at the organiser's discretion. No model-year list is published.
Displacement limit
600cc (S.1). S.2.1 permits the engine to be bored as long as the displacement does not exceed the class limit, so the figure is a ceiling on the engine as raced and not only as the factory built it.
Licence or tier
Not stated.
Minimum weight
Not stated.

Read from the same class section as the part answers. The rider side of the sport, tiers, ages, licences and what gets inspected, is set out across the bodies at Racing.

Open questions on this class (3)

Places where the rulebook contradicts itself, or where a figure could not be settled. Nothing in this list is decided, and it sits here rather than in a footnote because it is what you would want before spending money.

  • S.5.2 caps the pump and nozzle assembly at 139.7mm from the transom, expressed as an absolute distance rather than as a delta from OEM the way every other class states it. IJSBA's Vintage Ski carries the same 139.7mm figure expressed the same unusual way, which is worth noting and is not evidence either way about which document came first.
  • S.6.3 permits modifying the inner hull liner or deck to remove foam. Ski Modified forbids it. Neither rule is wrong and a generic answer would get one of them wrong.
  • The 650 and 701 variants exist only if an organiser offers them, so this record describes a class whose eligible craft list is partly outside the rulebook.

Sections this rulebook does not contain for this class

Confirmed absent by a targeted read rather than merely unnoticed. In a closed-list class an absent article is why a part reads as not permitted; in an open class it is why one reads as open.

  • No forced induction article.
  • No sponson article beyond the general J.16 rule.

What the rules say (61 parts)

18 permitted outright, 26 permitted with stated conditions, 1 refused by a rule we can quote, 1 held to the original part by a rule we can quote and 15 refused by our reading of the class rather than by a quoted rule. Grouped where the same rule gives the same answer, so two "Not legal" groups can sit side by side under different 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.
Not permitted, not listed in the rules
Treat it as coming off. The class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list, so this is our reading rather than a rule we can quote at you.
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.

Read the refusals as a list of work. Anything below marked Not legal, OEM part required, or Not permitted has to come off the machine, or go back to the standard part, before it races in this class.

Not legal1 part

Bolts, nuts and washers may not be substituted with titanium unless originally equipped. Locking mechanisms are allowed. J.7

OEM part required1 part

S.6.1 lets an aftermarket hood be used for hull modifications, yet no Vintage Ski clause says which modifications, so the only quotable allowance is J.13: repair or reinforcement within 2 mm (0.08 in) of the original configuration. J.1, J.13, S.6.1

Not permitted, not listed in the rules15 parts

On a closed list an unlisted modification is not permitted. A.2.2, J.1

Legal, with conditions1 part

An aftermarket flame arrester is allowed if it meets USCG, UL-1111 or SAE J-1928 Marine standards. S.3.2

Legal, with conditions1 part

Vintage Ski admits two-stroke craft, whose control unit is the CDI box, so S.4.1 lets it be aftermarket with no input or output beyond the original and no sensor added, while S.4.2 opens the rest of the ignition system, the RPM limiter bypass and total-loss ignition included. S.4.1, S.4.2

Legal, with conditions1 part

Gauges may be modified or removed provided no hazard is created and any resulting hole is sealed. Section J permits modification and removal and never addresses adding an aftermarket instrument. J.15

Legal, with conditions1 part

J.7, in the general rules for every class, names wiring as replaceable with aftermarket options, which overrides the closed-list default and covers replacement wiring. Connectors are not named on their own, and J.7 does not open added inputs or outputs, a different harness design or an ECU. J.7

Legal, with conditions1 part

Must remain OEM except: port modifications, internal surface changes, ignition/stator mounting area for aftermarket ignition, extra carb pulse-line fittings, drain removal or plugging. S.2.3

Legal, with conditions1 part

May be modified or replaced with an aftermarket part. The original diameter must be maintained in Stock class, and the rulebook never defines which classes that is. J.18.2

Legal, with conditions1 part

May be replaced within OEM specifications. J.18.3

Legal, with conditions1 part

Aftermarket or modified, full-length type with at least one bar parallel to the driveshaft, dropping no more than 12.00mm (0.47 in) below the flat plane of the pump intake. J.18.1

Legal, with conditions1 part

Aftermarket or modified. An extension may not exceed the width of the original plate, and on a ski may not extend more than 100 mm (3.94 in). J.18.1

Legal, with conditions1 part

Replacement trim plates may be used provided they mimic the handling characteristics of the stock plates. J.18.2

Legal, with conditions1 part

The inner hull liner or deck CAN be modified to facilitate foam removal - opposite of Ski Modified. S.6.3

Legal, with conditions1 part

Ventilation tubes may be altered, aftermarket, repositioned on the original ducting or removed, but inlet and outlet openings keep stock size, and vents may be covered or sealed with no other hood change, cover or cowling. S.6.2

Legal, with conditions1 part

Aftermarket, modified, repositioned or removed. Up to two, each no longer than 36 in (91.45 cm), protruding no more than 3.94 in (100 mm) horizontally, at least 6 mm thick with radiused leading edges, and not attached to a planing surface. J.16

Legal, with conditions1 part

Mat kits and padding are allowed in every class by the general rules (J.14), which overrides the closed-list default. Footholds and foot straps are not named there, so they stay not permitted. J.14

Legal, with conditions1 part

The handle pole assembly and mounting brackets may be modified or replaced provided original functionality is retained. Length may be altered and the attaching point reinforced. J.17.2

Legal, with conditions1 part

Replacement bumpers and side rails may be used provided they create no hazard. A permanently affixed nose bumper remains required. J.13, I.17

Legal, with conditions1 part

May be added to adjust handling. Constant mass only, and no other part may be modified to carry it. J.19

Legal1 part

J.7, in the general rules for every class, names hoses and clamps as replaceable with aftermarket options, which overrides the closed-list default and covers an aftermarket fuel hose. Fittings are not named on their own. J.7

Legal1 part

The ignition system may be modified or replaced with aftermarket parts, which takes in the trigger plate and timing, and no timing limit is stated. S.4.2

Legal1 part

On these two-strokes the flywheel is the magneto rotor that powers and triggers the ignition, so it is read as part of the ignition system that S.4.2 lets be modified or replaced with aftermarket parts, total loss ignition included. S.4.3 adds aftermarket or modified flywheel covers. S.4.2, S.4.3

Legal1 part

Ring number, type, and placement may be modified. S.2.1

Legal1 part

The cylinder head may be modified or replaced with an aftermarket one, with no dome, squish or compression limit stated. S.2.7

Legal1 part

May be replaced, as may starters and oil injection systems, with the oil injection system removable or disconnectable. J.8

Legal1 part

Titanium driveshafts are allowed in this class, as are titanium impeller housings and stator vane assemblies. Nothing else in titanium is, and the J.7 fastener ban still stands. S.5.1, S.5.2

Legal1 part

Aftermarket hoods may be used, and the clause ties that to hull modifications without saying more. S.6.1

Legal1 part

Aftermarket bulkheads are permitted, with no material or design limit stated. S.6.4

Legal1 part

Grips, throttle and cables may be modified or aftermarket. The bar must be padded at the mounting bracket or the crossbar padded. J.17.1

Legal1 part

Steering shaft, holder, handlebar holder and cables may be aftermarket, and quick-turn modifications are allowed. J.17.2

Legal1 part

The cooling system may be modified with aftermarket cooling lines and water bypass systems, provided no hazard is created for other riders. S.2.4

Legal1 part

The bilge pump may be modified or disconnected and aftermarket bilge draining systems are permitted, provided they create no hazard. J.10

IHRA 2026, S, read from the rulebook on 2026-09-11. Read the rule yourself. Every IHRA class · where the rulebooks differ · how this site reads a rulebook.

This is one class. Every part below also has a page of its own showing where it stands across every class this body runs, and legality by part is the index of them.

What we corrected here, and when

  • Footholds, foot straps and tray mats. Corrected 2026-10-02: the Ski Vintage row read the closed-list default and refused a mat kit, which J.14, in the general rules for all classes, allows.
  • High-pressure fuel line and fittings. Corrected 2026-10-02: the Ski Vintage row read the closed-list default and refused a fuel hose, which J.7 allows in every class; until 2026-10-31 this line wrongly excepted the drag section, where J.7 applies too.
Cite this page

“Ski Vintage, IHRA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ihra/ski-vintage/

Add the date you read it.

61 parts read · 18 permitted, 26 with conditions · 2026 rulebook

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