Rotax MAX Torque Settings: The Complete Table for the 125 MAX evo Engine
Updated: 3 days ago
A screw that is too loose comes undone and one that is too tight damages the thread or distorts a part. On the Rotax engine every screw has its own tightening value and you reach it with a torque wrench. Here you will find all the Rotax MAX torque settings of the Rotax 125 MAX evo repair manual (April 2024 edition), grouped by engine area and explained in plain words.
In short: to tighten the Rotax MAX engine correctly you need a torque wrench and the right value for each screw. Values are measured in Nm (newton metres), the number you set on the wrench. The most used: the 4 cylinder nuts go to 24 Nm, tightened crosswise; the spark plug to 27 Nm; the head cover to 10 Nm. The combustion chamber insert is tightened in two steps: first all screws to 5 Nm, then all to 30 Nm. Below you will find every value, area by area.
How to read the tables
Nm (newton metre): the tightening force. You set it on the torque wrench, which clicks when the screw reaches the right value.
Crosswise: the screws are tightened diagonally, a little at a time, like the wheel nuts of a car. This way the part sits evenly and does not distort.
M6x25: the size of the screw. M6 means 6 mm diameter, 25 is the length in mm.
LOCTITE 243 and LOCTITE 648: thread glues (threadlockers) that stop screws coming loose with vibration. 243 is medium strength and comes apart with normal tools; 648 is high strength and is used on parts that must never move.
SILASTIC: a sealant spread on the gasket to prevent leaks.
Rotax MAX torque settings: cylinder and head
Part | Torque | How to do it |
Cylinder studs screwed into the crankcase | 5 Nm | With LOCTITE 243 on the longer thread end |
Cylinder nuts (4) | 24 Nm | Crosswise |
Combustion chamber insert (5 screws) | 5 Nm, then 30 Nm | Two crosswise steps: first all screws to 5 Nm, then all to 30 Nm. Check that the O-ring stays in its groove |
Cylinder head cover (4 screws M6x25) | 10 Nm | Crosswise, with the O-ring in its groove |
Spark plug | 27 Nm | First screwed in by hand, then torque wrench |
Exhaust socket (2 screws M8x20) | 20 Nm | With a new gasket and SILASTIC on both sides |
Exhaust valve (Senior MAX only)
Part | Torque | How to do it |
Exhaust valve and its stud | 10 Nm | With LOCTITE 648, stud screwed in completely |
Valve rod housing (2 screws M6x25) | 10 Nm | Oil seal coated with engine oil; after tightening check that the valve moves freely |
Exhaust valve piston | 1.2 Nm | Very low value: tighten gently. The bellows must sit in its groove |
The valve piston is tightened to only 1.2 Nm: it is the lowest value on the whole engine and the easiest to get wrong. How the valve works is explained in The Rotax Exhaust Valve.
Intake, reed valve and fuel pump
Part | Torque | How to do it |
Reed valve, intake socket and bracket (5 screws M6x25) | 7 Nm | With the gasket on the cylinder |
Reed petal screws (M3x6) | 1.5-2 Nm | With LOCTITE 648 |
Fuel pump on the bracket (2 screws M6x20) | 10 Nm | With new lock nuts and washers |
Fuel pump bracket on the carburettor flange (3 screws M6x25) | 7 Nm | - |
Crankcase, clutch and starter
Part | Torque | How to do it |
Two crankcase halves (10 screws) | 10 Nm | Crosswise starting from the middle, with new gasket 650494 |
Gear cover (8 screws) | 10 Nm | With a new gasket and sealing washers |
Starter gear nut (M28x1) | 120 Nm | With LOCTITE 648 |
Clutch (3 screws M6x12) | 17 Nm | With LOCTITE 648 |
Nut joining clutch drum and sprocket | 100 Nm | With LOCTITE 648 |
Clutch drum nut on the crankshaft | 35 Nm | With LOCTITE 243; the washer goes with the machined side towards the drum |
Chain guard (3 screws M6x25) | 5 Nm | - |
Electric starter support (2 screws M6x35) | 10 Nm | - |
Screw on the opposite side of the starter (M6x30) | 10 Nm | Remember to fit the ground cable |
Ignition pick-up (2 screws) | 10 Nm | - |
Radiator on the engine (screw M8x75) | 24 Nm | With its washer |
Before fitting the clutch drum the manual reminds you to grease the crankshaft and the needle cage with lithium grease. Everything about the clutch in The Rotax MAX Clutch: How It Works, Wear and Maintenance.
The 4 rules of the Rotax manual
Always a torque wrench: by feel you never reach the right value.
Crosswise: cylinder nuts, combustion chamber insert, head cover and crankcase are tightened crosswise.
The right threadlocker: LOCTITE 243 where the part will come apart again, LOCTITE 648 where it must never move.
New gaskets: exhaust socket, cylinder and crankcase are always refitted with new gaskets.
Engine seal: what you can tighten yourself
Cylinder, head and exhaust valve are sealed engine parts: opening and closing them is work for the Rotax service centre. You can check the spark plug, radiator, fuel pump and chain guard yourself. What you can touch is explained in Rotax engine seal and regulations. For the right spark plug read Rotax MAX NGK Spark Plug.
Frequently asked questions
What is the Rotax MAX spark plug torque?
27 Nm. The spark plug is first screwed in by hand and then tightened with the torque wrench.
What torque for the Rotax cylinder nuts?
24 Nm, tightened crosswise on the four studs.
How is the combustion chamber insert tightened?
In two steps, always crosswise: first all 5 screws to 5 Nm, checking that the O-ring stays in its groove, then all to 30 Nm.
What are the Rotax MAX clutch torque settings?
The 3 clutch screws go to 17 Nm with LOCTITE 648. The clutch drum nut on the crankshaft goes to 35 Nm with LOCTITE 243.
What does tightening crosswise mean?
It means tightening the screws diagonally and a little at a time, like the wheel nuts of a car, so the part sits evenly and does not distort.
Do these Rotax torque settings also apply to the DD2?
No: the values come from the Rotax 125 MAX evo repair manual. The DD2 has its own repair manual.
Source: Rotax 125 MAX evo repair manual, April 2024 edition (BRP-Rotax).
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Read also: Rotax engine maintenance → · Rotax MAX NGK spark plug → · The Rotax MAX clutch → · How to measure squish on Rotax engines → · How to install a Rotax engine on a kart →
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Author: Sergio, TKS RaceLab | Published: 20 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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