Rotax engine seal and regulations: what you can touch
Updated: 3 days ago
In the Rotax world the engine is the same for everyone: it's the basis of the one-make series and the reason the driver makes the difference. To guarantee this there is the seal and a very precise technical regulation. Here is what the Rotax engine seal is, what you can adjust yourself and what is checked at scrutineering.
In short The Rotax engine is sealed by an authorised distributor or service centre with a steel cable and a numbered seal, recorded on the engine identity card. There's one golden rule: anything not expressly allowed is forbidden. On the carburettor the idle, needle and main jet settings are free, but the parts are the mandatory ones; NGK GR8DI or GR9DI spark plugs, 95-98 fuel and XPS Castor Racing 2T oil at 2% (1.5% on Micro and Mini in the Italian Rotax MAX Challenge) are mandatory.
What the Rotax engine seal is
The seal is a steel cable that runs through one intake flange screw, one cylinder stud and one cylinder head cover screw, closed with a seal crimped using the Rotax calliper. The legal seal is black anodised aluminium, with the ROTAX logo, a 6-digit serial number and a barcode. In the Italian Rotax MAX Challenge only seals with the Italian barcode are valid, and only engines imported by the Italian importer can race. That way nobody can open the engine without it showing.
The seal covers the complete engine, such as the Rotax 125 Senior MAX EVO engine and the Rotax 125 DD2 MAX EVO engine.
Who seals the engine and the identity card
• Who can seal it: only an authorised Rotax distributor or a service centre appointed by them, after checking the engine.
• The engine identity card: whoever seals it records the engine serial number, the seal number, a stamp and signature. The card stays with the engine owner.
• Registration: the engine must be registered and comply with the technical regulation.
• If the seal breaks: the engine must be fully checked against the technical specification and re-sealed by an authorised centre. At scrutineering you need an intact seal and a matching card.
The Rotax technical regulations: the golden rule
The Rotax technical regulations start from a simple principle: anything not expressly allowed is forbidden. Only genuine Rotax components designed for your class may be used, the engine and its ancillaries can't be modified, and thermal, ceramic or anti-friction coatings are banned. For everything outside the seal, the driver is responsible for compliance.
To understand which engine suits you read Rotax Senior vs DD2.
Carburettor: mandatory parts and free settings
• Mandatory parts: the carburettor must be the genuine Dell'Orto VHSB 34 XS carburettor, with VHSB 34 cast on the body, and only the parts set by the regulation go inside it, identified by their stamped number. They can't be swapped for other sizes.
• Slide and needle: slide with 45 in the casting and needle stamped K57: Dell'Orto carburettor slide 45 and Dell'Orto K57 needle.
• Needle jet and starter jet: needle jet stamped DP267 and starter jet stamped 60: Dell'Orto DP267 needle jet and Dell'Orto starter jet 60.
• Needle valve and floats: needle valve stamped 150 and two floats marked 4.0 g: Dell'Orto needle valve 150 and Dell'Orto 4.0 g floats.
• Other internal parts: all other internal parts must stay the genuine ones, marked as the regulation requires.
• Free settings: with the mandatory parts fitted, the idle and idle-air screws and the needle position can be adjusted freely.
• Main jet: any Dell'Orto main jet is legal, even if it isn't in the Rotax catalogue. Organisers can set a minimum main jet for each race, and jets must always be properly tightened. To have every size there's the Dell'Orto main jet kit.
• Vent hoses: the two vent fittings must be connected with the original hose, at least 155 mm long, the Dell'Orto carburettor vent hose 260260. The carburettor can be used with or without the fuel sieve.
Everything about the carburettor is in the guide to the Rotax Dell'Orto VHSB 34 XS.
Spark plug, fuel and oil: what the Rotax technical regulations say
• Spark plug: only NGK GR8DI or GR9DI, with a maximum electrode gap of 1.00 mm on Junior, Senior and DD2 and 1.20 mm on Micro and Mini: NGK GR8DI-8 spark plug and NGK GR9DI-8 spark plug. How to read it in the guide to the Rotax NGK spark plug.
• Fuel and oil: 95 to 98 octane unleaded petrol and XPS Castor Racing 2T oil at 2% (1.5% on Micro and Mini in the Italian Rotax MAX Challenge), mandatory. The right proportions are in the guide to the Rotax fuel mix.
• Fuel filter: between tank and pump there must be the Rotax-branded fuel filter.
• Gearbox oil: only XPS oil may be used, with no switching to other brands: XPS Kart Gear Oil for Rotax MAX and XPS Kart Gear Oil for DD2.
ECU, exhaust and gearing
• ECU: only the Dell'Orto ignition system is allowed. Officials can ask you at any time to replace the ECU and check it with the Rotax tester: Rotax MAX EVO ECU.
• Exhaust: the original Rotax exhaust system for your class is mandatory, such as the complete Rotax EVO DD2 exhaust.
• Gearing: on Micro and Mini the ratio is fixed: under the global Rotax regulations Micro 14/72 and Mini 13/80, in the Italian Rotax MAX Challenge 2026 Micro 13/80 and Mini 14/74. Always with a Rotax pinion and Rotax 219-pitch sprocket.
At technical scrutineering
Present the engine with an intact seal and the matching identity card. Officials can open and re-check the engine before or after the race, or in case of a protest. These are the Rotax MAX Challenge rules: national championships and races may have their own rules, so always check the regulations of your event. If you want to start racing, begin with the guide to the karting licence and keep the engine in good order with Rotax engine maintenance.
Frequently asked questions
What happens if the Rotax engine seal is broken?
The engine must be fully checked against the Rotax technical specification and then re-sealed by an authorised Rotax distributor or service centre. Without an intact seal and a matching identity card you won't pass scrutineering.
Which settings are free on the Rotax carburettor?
The idle and idle-air screws, the needle position and the Dell'Orto main jet size are free. The parts are mandatory instead: slide 45, needle K57, needle jet DP267, starter jet 60, needle valve 150 and 4.0 g floats.
Which spark plug and oil does the Rotax regulation require?
Only NGK GR8DI or GR9DI plugs, with a maximum electrode gap of 1.00 mm on Junior, Senior and DD2. XPS Castor Racing 2T oil at 2% is mandatory for the mix (1.5% on Micro and Mini in the Italian Rotax MAX Challenge).
Source: Global Rotax MAX Challenge Technical Regulation 2026 and its Bulletin 04.
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Read also: Rotax Senior vs DD2: the differences → · Rotax engine maintenance: routine and rebuild → · Rotax fuel mix: petrol and oil → · Rotax jetting in hot, cold and wet weather: what changes on track → · Rotax Plasma cylinder 2027: what changes → · How to measure squish on Rotax engines → · Rotax technical scrutineering →
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Author: Sergio, TKS RaceLab | Published: 18 October 2026
TKS RaceLab is the Italian online store dedicated to karting: spare parts, accessories and everything you need to get on track. With Arrive & Drive you arrive at South Garda Karting (Lonato), Franciacorta, Cremona or Ala and find your kart ready to go. No hassle, just driving.
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