BRP ROTAX 125 MAX DD2 evo Operation and maintenance manual

for ROTAX®-engines type
125 MAX DD2 evo
Part no.: 297 733 Edition: 09/2016
BRP-Rotax GmbH & Co KG | Rotaxstrasse 1 | 4623 Gunskirchen, Austria | T: [phone] | F: [phone]
www.rotax.com | www.rotax-kart.com
Installation instructions and
Operator‘s Manual

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General information
BRP-Rotax recommends products of the following companies:

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For information regarding the repair of the engine 125 MAX DD2 evo contact an authorized service
center or consult the workshop manual (available on the internet at www.rotax-kart.com).
We ask to hand over this manual, the engine identity card and the product and service
registration document to the new owner in case of a change of ownership.
Preface
This document and all technical data and procedures therein are property of BRP-Rotax GmbH &
Co KG and based on the state of knowledge at the time of publication. The manual has been
drawn up to the best of our knowledge. However, we exclude any liability.
We reserve all rights including technical modification and possibility of errors.
Reprinting, translation or copies in whole or in part, are authorized only after written permission by
BRP-Rotax GmbH & Co KG.
BRP-Rotax GmbH & Co KG reserves the right at any time to discontinue or change specifications,
prices, designs, features, models or equipment without incurring any obligations.
Engine performance may vary depending on, among other things, general conditions, ambient
temperature and altitude.

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Introduction
Congratulations on choosing the ROTAX engine Type 125 MAX DD2 evo.
The ROTAX engine Type 125 MAX DD2 evo has been developed exclusively for the use in go-
karts, which must only be run on specified tracks. This product has numerous technical
innovations.
pWarning: Before starting with installation and operation of the engine, observe the
installation instructions and Operator’s Manual and follow all instructions.
pWarning: This engine performs better than comparable products.
Repeating symbols
pWarning: Identifies an instruction, which if not followed may cause injury or endanger
the life of the driver, mechanic or third party.
¢Attention: Denotes an instruction which if not followed may severely damage the engine. Non-
compliance might lead to health hazards under certain conditions.
¿Note: Information useful for better execution and understanding of instructions.
ÆDenotes a working operation
PDenotes a checking operation
TIP This information gives you additional advice and tips
End of section:
End of chapter:

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INSTALLATION INSTRUCTIONS FOR ROTAX ENGINE TYPE
125 MAX DD2 evo

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Table of Contents of Installation Instructions
1. General................................................................................................................................... 6
2. Installation and connection of the fuel system................................................................... 7
2.1. Installation and connection of the fuel pump.................................................................... 7
3. Installation and connection of the carburetor..................................................................... 9
4. Installation of the Bowden cable for carburetor control................................................... 10
5. Installation of the mounting plate ...................................................................................... 12
6. Fitting of the spark plug...................................................................................................... 13
7. Installation and connection of the RAVE control unit ...................................................... 14
8. Check of oil level in gear box ............................................................................................. 17
9. Installation of overload clutch and engine with rear axle................................................. 19
10. Engine attachment to chassis ........................................................................................ 20
10.1. Engine attachment with engine brackets ....................................................................... 20
10.2. Direct attachment of the engine to chassis .................................................................... 21
11. Installation of the wiring harness................................................................................... 22
12. Installation of the battery and ECU ................................................................................ 26
12.1. Install ECU into the battery holder ................................................................................. 26
12.2. Installation of the battery................................................................................................ 28
13. Assembly of paddle shift system ................................................................................... 30
14. Installation of the radiator............................................................................................... 36
15. Installation of the intake silencer with integrated air filter ........................................... 38
16. Installation of the exhaust system ................................................................................. 39
17. Finishing work................................................................................................................. 41
17.1. Venting of the gear box.................................................................................................. 41

Installation Instructions 125 MAX DD2 evo
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1. General
pWarning: For the best possible engine operation, compliance with the following advice
regarding installation of engine and equipment is required.
pWarning: Engine operation is permitted only with equipment supplied by ROTAX.
pWarning: Modifications to engine or equipment are not allowed.
pWarning: Besides the engine-specific installation advice, also pay attention to
information of the respective chassis manufacturer.
¿Note: The registration document and engine identity card must be provided to the final
consumer upon delivery by the authorized service center with handover date and
company stamp.
¿Note: The data entered in the registration document and/or engine identity card is required
for the verification of a warranty claim. Without a completely filled-in engine identity
card, no warranty claim will be granted.
¿Note: In case of participating in the ROTAX MAX CHALLENGE (RMC), the engine must
be verified for conformity with the technical regulations and sealed.
The serial number of the seal must be entered in the engine identity card.

Installation Instructions 125 MAX DD2 evo
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2. Installation and connection of the fuel system
2.1. Installation and connection of the fuel pump
ÆThe retaining plate, rubber buffers, fuel pump and fuel hose (with 230 mm and
1800 mm length) are already pre-assembled. See Fig. 1.
Fig. 1
ÆInstall the retaining plate with the fuel pump (pos. 1) on the gearbox cover by using
2 screws M6x30 (pos. 3) and washers (pos. 2).
Fig. 2
TIP: Facilitate the assembly of the fuel hose by slightly widening the hose end with a pair
of circlip pliers.
¢Attention: Fuel hose can be damaged! Avoid excessive widening of the fuel hose.
Fig. 3
ÆThe fuel hose with 230 mm length will be connected later to the carburetor, see
carburetor installation in section 3.

Installation Instructions 125 MAX DD2 evo
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ÆThe larger fuel hose (pos. 1) should be connected to the fuel filter (pos. 2) and to
the fuel tank. See Fig. 4.
Fig. 4
¢Attention: Pay attention to the arrow’s direction on the fuel filter. This must point towards the
fuel pump.
¢Attention: Route the fuel line from the fuel tank to the fuel filter so that it does not touch any
moving parts or the track and attach the fuel line onto the top side of the chassis
tube.
¢Attention: The flow in the impulse hose and fuel lines must not be restricted by the use of
cable ties.

Installation Instructions 125 MAX DD2 evo
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3. Installation and connection of the carburetor
See Fig. 5.
ÆFit the carburetor (pos. 1) into the carburetor socket and secure with a hose clamp
(pos. 2) in vertical position.
ÆConnect the outlet hose of the fuel pump with the fuel inlet (pos. 3) on the
carburetor.
Fig. 5

Installation Instructions 125 MAX DD2 evo
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4. Installation of the Bowden cable for carburetor control
See Fig. 6.
ÆCarefully remove the carburetor cover and the rubber ring (pos. 7, 8).
¢Attention: Reset spring (pos. 6) of carb piston presses against carburetor cover and might
eject carburetor cover at removal.
ÆRemove nipple screw (pos. 5) with A/F 10 wrench from carburetor piston (pos. 2).
ÆEngage nipple of Bowden wire (pos. 9) in nipple screw (pos. 5).
ÆFit nipple screw in carburetor piston and hand-tighten with A/F 10 wrench.
ÆInsert carburetor piston (pos. 2) into carb body with recess of piston towards intake
silencer.
ÆPass Bowden wire through compression spring (pos. 6) and through cover with
rubber ring (pos. 7, 8) of carburetor.
ÆFit carb cover (pos. 7) on carburetor.
ÆPass Bowden wire through Bowden conduit and through adjustment screw on
chassis (throttle pedal).
ÆConnect Bowden cable to throttle pedal.
Fig. 6
¿Note: Shorten Bowden cable as required.

Installation Instructions 125 MAX DD2 evo
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ÆRoute the carburetor Bowden cable on the top side of the chassis tubes and attach
with the cable ties supplied. Make sure that the Bowden cable does not touch any
moving parts or the track.
pWarning: The carburetor Bowden cable must not be kinked or restricted as the
carburetor piston might get stuck in full throttle position.
ÆSet and secure the adjustment screw for Bowden cable on chassis so that the
carburetor piston will remain in closed position when throttle pedal is not activated.
ÆSet and secure the stop screw for throttle pedal so that, with pedal completely
pressed down, the carburetor piston will be in fully open position. The bowden cable
must not be under full tension when the throttle is in fully open position.

Installation Instructions 125 MAX DD2 evo
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5. Installation of the mounting plate
ÆThe holding bracket, the mounting plate, the solenoid valve and the ignition coil are
already pre-assembled.
ÆInstall whole bracket kit with Allen screw M8x50 (pos. 2) and distance sleeve
8.2/12/25.5 (pos. 3) onto the engine.
¢Attention: Slot (pos. 1) of retaining plate has to be installed in the correct position.
Fig. 7
¿Note: Distance sleeve (pos. 3) has to be installed between engine housing and retaining
plate. Distance sleeve can be replaced by the fitting of an additional seat stay.

Installation Instructions 125 MAX DD2 evo
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6. Fitting of the spark plug
See Fig. 8
The engine will be supplied with a spark plug of the type NGK Iridium.
ÆRemove the transport plug from the cylinder head.
ÆCheck electrode gap of spark plug. Adjust as required.
¿Note: The electrode gap of the spark plug should be 0,7 mm (0.027 in) to 0,8 mm wide
(0.032 in) (for NGK spark plugs). Only slight bending of the ground electrode is
permitted.
ÆFit supplied spark plug (pos. 1) and tighten 25 Nm (221 lbf in) to 27 Nm (239 lbf in).
ÆInstall the spark plug connector (pos. 2), ensure correct engagement.
Fig. 8

Installation Instructions 125 MAX DD2 evo
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7. Installation and connection of the RAVE control unit
¿Note: The hose package of the RAVE control is already pre-assembled.
¿Note: The impulse restrictor is offered optionally.
Insert impulse nozzle (pos. 6) about 25 mm into the 420 mm pressure line (pos.
7) using an Allen key SW4. Pay attention to the mounting direction! It also works
without an impulse nozzle, this only serves to choke the opening of the exhaust
valve.
¿Note: In order to prevent the displacement of the impulse nozzle (pos. 6), a small cable tie
(pos. 8) should be attached directly afterwards to the pressure line. Do not tie up the
pressure line completely!
Fig. 9
Fig. 10
ÆAttach the black hose of the hose package (pos. 1) to the metal connector (pos. 2)
of the magnetic valve.

Installation Instructions 125 MAX DD2 evo
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Fig. 11
ÆAttach the other end of the hose package (pos. 1) (short end with T-piece) to the
fuel pump.
Fig. 12
ÆAttach the fuel line of the hose package (pos. 1) to the impulse nipple on the engine
housing.
¿Note: Check that valve is not the lowest point of the impulse circuit to prevent that.
condensation affects a proper operation.
Fig. 13
ÆAttach cable tie wrap with mount (pos. 1) to the housing. See Fig. 14.

Installation Instructions 125 MAX DD2 evo
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Fig. 14
ÆSecure both lines with a cable tie, ensuring that the black hose (pos. 2) is on top.
See Fig. 15.
¢Attention: Do not tighten cable ties too tight, because consricted lines can lead to loss of
function.
ÆAttach an additional cable tie (pos. 3) as shown in Fig. 15
Fig. 15
ÆAttach the 220 mm pressure line (pos. 1) to the magnetic valve (pos. 3). Secure
the pressure line on the magnetic valve with a tie wrap (pos. 4). Attach the other
end of the pressure line to the exhaust valve (pos. 2).
Fig. 16

Installation Instructions 125 MAX DD2 evo
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8. Check oil level in gear box
The gear box is already filled with the appropriate amount of oil 150 cc (0.039 gal.) by the engine
manufacturer. However, before the engine is installed in the frame, the oil level must be verified or
replenished.
ÆPlace engine on a horizontal surface and/or assembling trestle.
¢Attention: When placing the engine on a horizontal surface, take care not to damage the
crankcase sensor, which is mounted on the bottom of the crank case.
ÆThe oil level can be checked on the inspection glass (pos. 1). It should reach
approximately to one third of the inspection glass, see Fig. 32. If the oil level is not
sufficient, replenish oil as described in the following steps.
Fig. 32
¿Note: Oil capacity (total): 150 cc (0.039 gal)
¿Note: Specification of gear oil: engine oil SAE 15W-40.
ÆRemove the air vent screw (pos. 1, Fig. 33) and slowly fill in oil of specification SAE
15W-40 until oil level is in the middle of the inspection glass.
ÆHand-tighten air vent screw (pos. 1).
Fig. 33

Installation Instructions 125 MAX DD2 evo
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¿Note: For draining the oil from the gear case, remove the magnetic oil drain plug (pos. 1)
and sealing ring (pos. 2). Clean the oil drain plug before installation. Always use a
new sealing ring.
Fig. 34
¿Note: Tighten magnetic oil drain plug (pos. 1) to 20 Nm (177 lbf.in.).
pWarning: Do not run the engine without gear oil. This will lead to engine failure.

Installation Instructions 125 MAX DD2 evo
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9. Installation of overload clutch and engine with rear axle
¿Note: The overload clutch is the link between the engine and the rear axle of the kart. In
case that the rear axle has been blocked by (e.g. braking), the overload clutch is
slipping slightl, and is not transferring the peak load from the rear axle to the engine.
The bushings (pos. 2) are inside the overload clutch (pos. 1).
Fig. 35
ÆSlide the clamp ring (pos. 1), Fig. 36, the thrust washer (pos. 2), Fig. 36 and the
overload clutch (3) to the middle of the rear axle.
¿Note: The rear axle of the kart must have a smooth surface (no grooves for keys) in the
area of the 4 bushings of the overload clutch.
¿Note: Do not tighten the overload clutch and clamp ring yet (see section 10.1 Engine
attachment with engine brackets).
Fig. 36