Not legal1 part
Cylinder port modification beyond the 1.00mm / 30-degree chamfer is prohibited.
IJSBA · sport
Sport Spec
IJSBA2024, none - this document uses ALL-CAPS section headings, not numbered rules. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.
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.
- This document uses ALL-CAPS section headings rather than numbered rules. Do NOT invent SPSP.x rule numbers.
- 2024 document, may have been superseded for 2025.
- The Model Homologation listing on pages 10-11 did not come through and should be retrieved separately.
- A pre-launch note on the WaveBlaster in this class was supplied on 2026-09-10 and is held at docs/reference/sport-spec-prelaunch-note.md. It is NOT this rulebook, it cites APBA limits where this document cites none, and it predates the class in its own words. Its 1mm overbore limit matches this record exactly, which is either the idea surviving into the sanctioned rules or the note being closer to IJSBA than its APBA references suggest. Unattributed, so nothing from it is published.
- Polaris Hurricane displacement ceiling is not stated.
- The four-sponson allowance is unusual relative to the other two Sport/Freestyle classes.
What the rules say (49 parts)
41 permitted outright, 1 answered by our reading of the class rather than by a quoted rule, 1 the rules do not settle. Grouped by the answer, because an open class gives one answer to most questions and printing it once per part would say the same sentence forty times.
Not permitted, not listed in the rulesOur reading, not a rule we can quote at you. This class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list.
Not legal1 part
Titanium driveshafts prohibited.
Not legal1 part
Explicitly prohibited by this class document.
- Rider-controlled or automatic trim tab system · Hull and handling
Not legal1 part
No allowance for aftermarket hulls.
- Aftermarket hull or top deck · Hull and handling
OEM part required1 part
Flywheels must be OEM stock and unmodified as supplied from the factory. Sea-Doo HX must use the OEM unmodified 720 flywheel.
- Aftermarket or lightened flywheel · Ignition
OEM part required1 part
OEM stock seat base required. Height may be changed and/or covered.
- Aftermarket seat assembly / seat base · Hull and handling
Not permitted, not listed in the rules1 part
Not listed in this class document. Illegal under the closed-list principle.
- Stinger reducer insert + cooling line · Exhaust
The rules do not say1 part
Not addressed in this class document.
- Replacement wear ring · Driveline
Legal, within limits2 parts
Permitted subject to the universal limits in ijsba-globals.yaml constants.
Legal, within limits1 part
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.
Legal, within limits1 part
Model-specific.
- Aftermarket exhaust manifold / head pipe · Exhaust
Legal, within limits1 part
Kawasaki, Yamaha and Polaris may relocate and replace with aftermarket. Sea-Doo HX must use an OEM factory HX waterbox with water fittings plugged.
- Aftermarket waterbox · Exhaust
Legal, within limits1 part
Exit may be relocated to the hull rear; outlet flap may be removed.
Legal, within limits1 part
Polaris Hurricane and Yamaha Waveblaster carburetors may be modified or aftermarket. SEA-DOO HX MUST RETAIN STOCK CARBURETORS (rejetting and de-choking only).
Legal, within limits1 part
Allowed on Polaris Hurricane, Kawasaki X2 05-07 and Yamaha Waveblaster. Sea-Doo HX must keep the OEM manifold with factory line connections aligned as from the factory.
- Aftermarket intake manifold · Fuel
Legal, within limits1 part
Max 4 psi with automatic shutoff.
Legal, within limits1 part
Yamaha CDI modified or aftermarket provided timing is NOT manually adjustable. Kawasaki Gen 2 (2005-2007) CDI may be programmable. Advancing timing at the stator plate is prohibited on every model.
- Aftermarket CDI / ignition box (2-stroke) · Ignition
Legal, within limits1 part
Must fit the OEM battery box and be securely fastened. GP/Open/Freestyle/Sport GP additionally allow an additional battery, a new box and relocation.
- Replacement battery · Electrical
Legal, within limits1 part
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.
- Aftermarket cylinder (2-stroke) · Engine
Legal, within limits1 part
Compression capped: Kawasaki and Yamaha max 190 psi with min 0.040 in squish; Sea-Doo HX max 175 psi with min 0.051 in squish. Drop-down style domes prohibited on all models.
- Aftermarket cylinder head (2-stroke) · Engine
Legal, within limits1 part
Must retain original port timing, dome profile, skirt length/shape and material type, and weigh within +/-5.00% of OEM. Note this is 5%, tighter than the 25% used elsewhere.
- Aftermarket piston assemblies · Engine
Legal, within limits1 part
Stroke and rod length may NOT change. +/-5.00% assembly weight. Non-ferrous metals prohibited.
Legal, within limits1 part
Non-ferrous prohibited; rod length may not change.
- Aftermarket connecting rods · Engine
Legal, within limits1 part
STATOR VANE ASSEMBLY MUST REMAIN OEM STOCK. Pump mounting plate and shoe may be aftermarket. Sea-Doo HX may use the OEM plastic pump housing if it retains the small-diameter hub and vane count.
Legal, within limits1 part
No spacers or extended nozzles that push past 50.00mm.
Legal, within limits1 part
Extension may not be wider than the OEM plate, sides must be connected and radiused, and no fins, rudders or skegs. Max extension beyond the OEM plate: 100.00mm (3.94 in) Ski and Sport, 177.80mm (7.00 in) Runabout.
- Aftermarket pump cover plate / extension · Driveline
Legal, within limits1 part
Full-length type with at least one bar parallel to the drive shaft, all leading edges radiused, extending no more than 12.00mm (0.47 in) below the flat plane of the pump intake area.
- Aftermarket intake grate · Driveline
Legal, within limits1 part
Up to FOUR. Single- or two-sponson configuration per side limited to 1,524mm.
- Aftermarket sponsons · Hull and handling
Legal, within limits1 part
The handlebar must be padded at the mounting bracket, or the crossbar padded if fitted. This is a tech-inspection item.
- Aftermarket handlebars, throttle, throttle cable, grips, switches · Hull and handling
Legal, within limits1 part
Padding and/or mat kits may be added in every class. Where footwells exist they must be BLOCKED OFF during competition with no indentation into the footwell sides.
- Footholds, tray mats, padding kits · Hull and handling
Legal, within limits1 part
Ventilation tubes may be modified, relocated or removed. Polaris Hurricane hood/mirror cowling may be replaced provided it creates no additional airflow. NO OTHER hood modifications permitted.
- Aftermarket hood / engine cover · Hull and handling
Legal, within limits1 part
Replacement bumpers allowed provided no hazard is created. A soft flexible water-spray deflector may attach to the hull sides or bond flange, not extending beyond the perimeter of the OE bumper or side moldings as measured by plumb line. A permanently affixed IJSBA-approved nose bumper is REQUIRED under GEN.8.12.
- Replacement bumpers and water-spray deflectors · Hull and handling
Legal, within limits1 part
Allowed in essentially every class. Universal prohibitions: no manually controlled devices that alter cooling water flow during operation, no electronically controlled valves or water injection unless original equipment, and in most stock classes no NEW fittings added to the cylinder head, cylinder or crankcase.
Legal, within limits1 part
Fixed-type or automatic valves only. Thermostats, pressure regulators and solenoids qualify. Manual actuation of any kind during operation is prohibited everywhere.
Legal, within limits1 part
Constant mass only, within the normally exposed areas of the hull, creating no hazard and requiring no modification or relocation of other parts. Water and any other fluid ballast is prohibited in every class.
- Ballast weight kits · Hull and handling
Legal3 parts
Explicitly permitted by this class document.
- Aftermarket reed cage / block assembly · Fuel
- Aftermarket impeller at OEM diameter · Driveline
- Aftermarket nozzle trim system (pump-mounted) · Driveline
Legal1 part
Rejetting and de-choking explicitly allowed on all models including the HX.
Legal1 part
Reed valve assemblies modified or aftermarket, reed spacers permitted.
- Aftermarket reed petals · Fuel
Legal1 part
Must meet USCG, SAE J-1928 Marine or UL-1111 Marine backfire flame arrester standards.
- Aftermarket flame arrester · Fuel
Legal1 part
Modified or aftermarket filler cap allowed provided no hazard is created. The FILLER and RELIEF VALVE themselves must stay OEM.
- Aftermarket fuel filler cap · Fuel
Legal1 part
Aftermarket spark plugs of a different heat range are allowed in every class that addresses them.
- Aftermarket spark plugs of a different heat range · Electrical
Legal1 part
Fixed-position only.
- Aftermarket FIXED-position trim tab / ride plate extension · Hull and handling
Legal1 part
Aftermarket steering shaft, steering shaft holder, handlebar holder and steering cables are allowed. Quick-turn modifications that alter the steering ratio are allowed in most stock classes.
- Aftermarket steering shaft, shaft holder, handlebar holder, steering cables · Hull and handling
Legal1 part
The original bilge pump may be modified or disconnected and aftermarket bilge draining systems are allowed, provided no hazard is created.
- Aftermarket bilge draining system · Hull and handling
Legal1 part
Replacement engine mounts are allowed in every class that addresses them. Ski GP, Vintage and Freestyle additionally allow a modified or aftermarket ENGINE BED with the engine repositioned in the hull.
Legal1 part
Replacement starter motor and bendix are allowed in every class that addresses them.
- Replacement starter motor and bendix · Electrical
IJSBA 2024, none - this document uses ALL-CAPS section headings, not numbered rules, read from the rulebook on 2026-09-07, not verified by a racer. Read the rule yourself, Sport Spec. Every IJSBA class · where the rulebooks differ.
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.
49 parts read · 41 permitted outright · 2024 rulebook