Not legal1 part
Only replaceable jets, needle valve and needle valve spring changes, choke removal and an aftermarket primer. SSK.4.2
IJSBA · ski
Ski Stock
IJSBA 2025, SSK. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.
Read out of the published IJSBA rulebook on 2026-09-07, so confirm anything that decides a purchase. The full note is at the foot of the page.
Running the class
- Eligible craft
- Exclusively the 1500cc-based Kawasaki SX-R. OEM hull only.
- Displacement limit
- 1500cc (SSK.3.1). SSK.3.1 permits the engine to be bored and requires the displacement not to exceed the class designation, so the figure is a ceiling on the engine as raced and not only as the factory built it.
- Licence or tier
- Not stated. Junior competitors must use an IJSBA-approved restrictor plate.
- Minimum weight
- Not stated in this document.
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.
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.
- Model-year range for the eligible SX-R is not enumerated.
- Total sponson length printed as 1,524mm paired with "(90 in.)". 1,524mm = 60 in. One of the two figures is wrong in the source.
- No exhaust, fuel-tank, seat/tray, ride-plate, weight or racing-number rules exist in this document.
- Whether flywheel modification is addressed in SSK.5 could not be confirmed.
What the rules say (53 parts)
11 permitted outright, 15 permitted with stated conditions, 6 refused by a rule we can quote, 6 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
Only reprogramming of the original ECU is allowed. SSK.5.2
- Aftermarket standalone ECU · Ignition
Not legal1 part
Only the 1.00mm / 30-degree chamfer. Abrasive port cleaning is prohibited.
Not legal1 part
No internal modification of driveline components including pump stator and reduction nozzle. SSK.6.2
Not legal1 part
Only ventilation tube changes. Enlarging inlet or outlet openings is prohibited. SSK.2.12
- Aftermarket hood / engine cover · Hull and handling
Not legal1 part
Aftermarket hulls prohibited.
- Aftermarket hull or top deck · Hull and handling
OEM part required1 part
Replacing fuel injectors is prohibited. SSK.4.3
- Aftermarket fuel injectors · Fuel
OEM part required1 part
Replacing the fuel pump is prohibited. SSK.4.3
OEM part required1 part
No throttle body change is listed, and the intake rule bars any change to the airflow downstream of the airflow sensor. SSK.1.1, SSK.4.1
OEM part required1 part
Crankshaft must remain stock. SSK.3.2
OEM part required1 part
Camshaft replacement prohibited. Only bearings, timing changes and adjustable sprockets allowed. SSK.3.3
- Aftermarket camshafts · Engine
OEM part required1 part
The hull may be repaired but not otherwise modified, and a repair may not alter the original configuration by more than 2.00mm (0.08 in.). SSK.2.2
- Modification of the OEM hull · Hull and handling
Not permitted, not listed in the rules10 parts
Not listed in this class document. Illegal under the closed-list principle.
- Aftermarket waterbox · Exhaust
- Through-hull exhaust outlet / relocation kit · Exhaust
- Aftermarket intake manifold · Fuel
- Aftermarket connecting rods · Engine
- Supercharger rebuild internals, clutch, belt, pulleys · Forced induction
- Aftermarket intercooler · Forced induction
- Titanium driveshaft, impeller housing or stator vane assembly · Driveline
- Aftermarket nozzle trim system (pump-mounted) · Driveline
- Rider-controlled or automatic trim tab system · Hull and handling
- Hull extension · Hull and handling
Not permitted, not listed in the rules1 part
No exhaust section exists in SSK.
- Aftermarket exhaust manifold / head pipe · Exhaust
Not permitted, not listed in the rules1 part
No fuel tank section exists.
Not permitted, not listed in the rules1 part
No flywheel change is listed: the four-stroke ignition section opens only replacement batteries, ECU reprogramming and spark plugs, and changes not listed are not permitted. SSK.1.1, SSK.5
- Aftermarket or lightened flywheel · Ignition
Not permitted, not listed in the rules1 part
No clause allows a turbocharger or supercharger, changes not listed are not permitted, and the intake rule bars any change to the airflow downstream of the airflow sensor. SSK.1.1, SSK.4.1
- Aftermarket turbocharger or supercharger · Forced induction
Not permitted, not listed in the rules1 part
Not listed in this class document, so illegal under the closed-list rule (SSK.1.1); SSK.6.2 also bars internal modification of the reduction nozzle.
Legal, with conditions1 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, with conditions1 part
Must retain OEM compression ratio, dome profile, skirt length/shape and material type; weight within +/-25.00% of OEM. Non-conforming skirt shapes only with written IJSBA approval.
- Aftermarket piston assemblies · Engine
Legal, with conditions1 part
Max 1.00mm (0.04 in) at max 30 degrees.
Legal, with conditions1 part
Modified or aftermarket impeller retaining ORIGINAL DIAMETER. SSK.6.1
- Aftermarket impeller at OEM diameter · Driveline
Legal, with conditions1 part
Replacement wear rings within OEM INTERNAL DIAMETER specification.
- Replacement wear ring · Driveline
Legal, with conditions1 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, with conditions1 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, with conditions1 part
Up to FOUR sponsons. Max 38.00mm below the hull side/bottom intersection.
- Aftermarket sponsons · Hull and handling
Legal, with conditions1 part
Replacement trim PLATES only, replica parts offering the same handling characteristics as stock. Material may differ from OEM.
- Aftermarket FIXED-position trim tab / ride plate extension · Hull and handling
Legal, with conditions1 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, with conditions1 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, with conditions1 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, with conditions1 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, with conditions1 part
Fixed-type or automatic valves only. Thermostats, pressure regulators and solenoids qualify. Manual actuation of any kind during operation is prohibited everywhere.
Legal, with conditions1 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
Legal1 part
Carburetor jets (replaceable type), needle valves and needle valve springs may be changed. SSK.4.2
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
Reprogramming of the original ECU with no additional inputs or outputs and original connections retained. SSK.5.2
- ECU reflash / reprogramming of the OEM unit · Ignition
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
Valve springs and valve spring retainers allowed; replacement valves and seats at OEM weights and dimensions.
Legal1 part
Modified or aftermarket handlepole and mounting bracket, provided it functions as originally designed. Attaching point may be reinforced. SSK.2.9
- Aftermarket handlepole / pole bracket · 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 2025, SSK, read from the rulebook on 2026-09-07. Read the rule yourself, Ski Stock. Every IJSBA 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.
Cite this page
“Ski Stock, IJSBA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ijsba/ski-stock/
Add the date you read it.
53 parts read · 11 permitted, 15 with conditions · 2025 rulebook