Aixro XR50 User manual

OPERATION MANUAL

© Aixro GmbH / Woelfle Engineering GmbH 1/23
1. INTRODUCTION
1.1. Foreword
We would like to thank you for purchasing your new Aixro XR50 4-stroke rotary karting en-
gine. By doing so, you have helped set new standards for driving performance and environ-
mental responsibility.
! But before getting started, it is imperative that you read and understand instructions
and procedures outlined in this operator manual!
You will obtain important safety advice and information about the correct installation, first
launch and service of the engine.
We wish you lots of fun!
Aixro GmbH Woelfle Engineering GmbH
Münsterstraße 44 Randstraße 109
52076 Aachen 47804 Krefeld
Germany Germany
(production) (distribution)
www.aixro.de www.woelfle-engineering.com

© Aixro GmbH / Woelfle Engineering GmbH 2/23
1.2. General Safety Instructions
! The XR50 is one of the fastest karting engines available, and it might take some get-
ting used to. Please remember to be safe, brake early, and never drive faster than you
can control.
! The XR50 is made exclusively for kart racing. Using the engine in other applications is
strictly prohibited without our express written consent. Race the XR50 on designated
karting tracks only, so you never run the engine at full throttle for more than 10 con-
secutive seconds.
! The exhaust can become very hot, over 1000°C! Avoid any contact when hot.
! Always use a kart with front and rear brakes.
! Always keep your kart and engine in a good, clean condition. This helps detect defects
earlier and avoid dangerous accidents.
! You will find further (safety) advice in this manual, marked by “!”. Please read each of
these tips carefully. If you have any questions, please contact your dealer, our Ameri-
can importer RENNtech or us BEFORE you run the engine.
1.3. Development Stage
The operation manual is based on the state of knowledge at the time of publication. It was
produced to best knowledge, however excluding any liability. The specifications may deviate
from the actual performance due to production-related and external conditions.
The information presented in this manual is subject to change without notice.
1.4. Copyright, circulation, date of issue
All rights reserved.
The circulation or duplication of this document, even in extracts, is not permitted without ap-
proval by Aixro GmbH or Woelfle Engineering GmbH.
Title: Aixro XR50 Operation Manual
Edition 4.6 Aachen/Krefeld: June 2011

© Aixro GmbH / Woelfle Engineering GmbH 3/23
2. TABLE OF CONTENTS
1. INTRODUCTION..............................................................................................................1
1.1. Foreword ...................................................................................................................1
1.2. General Safety Instructions........................................................................................2
1.3. Development Stage...................................................................................................2
1.4. Copyright, circulation, date of issue ...........................................................................2
2. TABLE OF CONTENTS....................................................................................................3
3. ABOUT THE XR50...........................................................................................................4
4. ASSEMBLY ......................................................................................................................5
4.1. Cooling System..........................................................................................................5
4.2. Engine Mounting and Chain Tension.........................................................................5
4.3. Carburettor / Fuel Supply...........................................................................................6
4.4. Throttle Cable............................................................................................................7
4.5. Exhaust .....................................................................................................................7
4.6. Electrics.....................................................................................................................8
4.7. Data Acquisition.......................................................................................................10
5. FIRST LAUNCH..............................................................................................................11
5.1. Water.......................................................................................................................11
5.2. Fuel .........................................................................................................................11
5.3. Refuel / System Fill..................................................................................................11
5.4. Control.....................................................................................................................11
5.5. Start Preparation......................................................................................................11
5.6. Engine Start / Test Run............................................................................................12
6. OPERATION ..................................................................................................................13
6.1. Preparation / Control................................................................................................13
6.2. Starting / Heating Up On Track................................................................................13
6.3. Driving .....................................................................................................................14
6.4. Shut Down...............................................................................................................15
6.5. Transportation .........................................................................................................15
7. SERVICE AND MAINTENANCE.....................................................................................16
7.1. Clutch Bearings / Drive Sprocket.............................................................................16
7.2. Friction Discs / Clutch Plates ...................................................................................17
7.3. Air Filter Red Filter for Aixro and Dell’Orto Carburettors...........................................17
8. TROUBLESHOOTING....................................................................................................18
8.1. Engine Dropout........................................................................................................18
8.2. Engine Stutters........................................................................................................18
8.3. Lean Bottom End................................................. Fehler! Textmarke nicht definiert.
8.4. No Engine Start .......................................................................................................18
8.5. Dripping Carburettor / Overflow ...............................................................................19
8.6. Engine Suddenly Lean.............................................................................................19
9. TUNING..........................................................................................................................20
9.1. Driving in Rain .........................................................................................................20
9.2. Clutch Adjustment....................................................................................................20
9.3. Carburettor Adjustment............................................................................................20
10. TECHNICAL SPECIFICATIONS.....................................................................................21
10.1. Engine Data.............................................................................................................21
10.2. Fastening Torque.....................................................................................................21
10.3. Operating Fluids ......................................................................................................21
11. WARRANTY / LIABILITY................................................................................................22
11.1. Liability ....................................................................................................................22
11.2. Warranty Grant........................................................................................................22
11.3. Warranty Procedure.................................................................................................22

© Aixro GmbH / Woelfle Engineering GmbH 4/23
3. ABOUT THE XR50
The Aixro XR50 is a rotary engine based on the Wankel principle. Its main components are
Rotor with seals (equivalent to the piston with rings of a reciprocating piston engine)
Eccentric shaft (equivalent to the crankshaft)
Housing, also called trochoid due to its oval-like epitrochoid shape
side plates, closing the sides of the housing
The engine is a 4-stroke suction engine. Its rotor has a triangular shape, and the edges of
the rotor are in permanent contact with the trochoid through the apex seals. This creates
three separate combustion chambers along the flanges of the rotor and allows three 4-stroke
processes to run simultaneously. The rotor only rotates at 1/3 of the speed of the eccentric
shaft, so with every rotation of the shaft a different combustion chamber passes the spark
plug.
The processes within the engine, especially the long timings, lead to favourable emissions,
which can be as low as 1% of comparable 2-stroke engines and reach best 4-stroke level in
the driving cycle. The engine can be operated with a catalytic converter.
The XR50 uses a carburettor and fuel lubrication at a ratio of 50:1. Contrary to a two-stroke
engine the oil burns without residues.
To access the combustion chamber the fresh gases first flow though one side plate. Then
they flow through the rotor and the eccentric shaft in axial direction to reach the opposing
side plate. From there they access the combustion chamber. This cools and lubricates the
rotor, main bearing and eccentric shaft. At approx. 5500rpm a vacuum-controlled butterfly
valve opens a second channel of the split inlet port to allow additional gases to flow directly
into the combustion chamber. These cold fresh gases lead to the enormous power of the
XR50.
The particular advantages of the XR50 are its lack of vibration due to balanced rotating
masses, its very compact design, the extreme performance with a very flat torque curve, as
well as very low emissions. In addition the service performance is enormous for a racing en-
gine, and it has long times between overhauls.

© Aixro GmbH / Woelfle Engineering GmbH 5/23
4. ASSEMBLY
4.1. Cooling System
The XR50 uses a standard karting radiator and a conventional water pump, which is driven
by the rear axle, as well as standard karting water hoses.
1. Place the engine on your kart without bolting it down. This makes it easier to access
the water connections.
2. Mount the radiator without strain (usually on the left side of the kart). The radiator
should be mounted vertically enough to allow sufficient air flow through the system.
3. Connect one water hose at the lower connection of the radiator and the centre connec-
tion of the water pump.
4. Connect the radial connection of the pump with the lower connection at the front of the
engine with another hose.
5. Connect a third hose at the water connection on the backside of the engine (next to the
exhaust manifold) and the top of the radiator.
6. Fasten all connections with proper hose clamps.
! Ensure that the hoses are positioned far enough away from the exhaust to avoid melt-
ing or cooking, and secure them with tie wraps if necessary.
! Make sure that there are no kinks or sharp bends in the hoses, and that they do not
touch any moving parts or the ground.
! Note the rotation direction of the water pump.
4.2. Engine Mounting and Chain Tension
The XR50 is supplied with standard engine mounts, which fit most karts (Ø32mm x 92mm).
Engine mounts for different tube distances or diameters are available upon request. Only use
highest-quality chains and one-piece sprockets, type 428.
! Be sure that your engine mounts and clamps have the right dimensions. Otherwise
you may damage your kart and the engine.
1. Install the engine mounts if they are not yet assembled to the engine (usually ship in-
stalled; 4 countersunk screws M8x25 at 26Nm).
2. Remove the clutch cover (4 Allen screws –1x M6x20, 3x M6x10 –note the positions of
the screws), and mount the engine on the chassis.
3. Choose a suitable sprocket for your race track, and bolt it to the sprocket carrier.
4. Attach the engine to the kart with matching engine clamps.
5. Adjust the alignment between the front (clutch) and rear sprocket by moving the
sprocket carrier. Use a straight edge or alignment checking device as your guide.
6. Generally the engine should be positioned as close as possible to the rear axle to
achieve a short chain length. Therefore release the engine clamps again, (if applicable)
screw the engine support screw, which is attached to the chassis, as far to the rear
axle as possible, and put a preferably short chain around the sprockets.
7. Position the engine, so the chain has approx. 5mm “slack”, and tighten the engine
clamps.
8. After tightening the clamps the chain tension should be checked at different positions of
the rear axle. The chain must not be completely tight, but has to remain movable.
9. Now (if applicable) tighten the engine support screw, and re-attach the clutch cover
10. Install a standard chain guard (splash guard for the chain lubricant).
! Over-tightening the chain and worn components can build up heat. This significantly
reduces the life expectancy of the clutch, especially the friction discs and the clutch
bearing.
! A too loose or too long chain (chain slack >10mm) can also wear components.
! O-ring chains only run smoothly in use. Until an O-ring chain heats up, the load on the
clutch is higher. Therefore never use an O-ring chain with a 10T drive sprocket.

© Aixro GmbH / Woelfle Engineering GmbH 6/23
! Never use a chain lock. The chain must be riveted.
! Do not use a gear ratio shorter than 11:53. A shorter gear ratio will not make you
faster, but it will still increase the load on the engine and the tyre wear.
If you know the transmission ratio of a Rotax Max 2-stroke engine with a 12T sprocket, you
can use it as a guideline. Divide the number of teeth of the rear sprocket by 1.75, and you
have a first idea of the sprocket you need in combination with the standard 11T sprocket of
the XR50. e.g. RMax: 12/79  79:1,75 ≈ 45  XR50: 11/45
If the chain is assembled, the chain alignment can be controlled by checking the position of
the chain on the sprocket. In every position of the sprocket the chain must have slight space
to the sprocket on both sides. This also ensures that the sprocket is not warped.
4.3. Carburettor / Fuel Supply
The fuel tank should have two connectors. One connector needs to have a line on the back-
side, which leads to the bottom of the tank (a standard design for karting fuel tanks), while
the other one must not have a tube on the backside. If the fuel tank should have a third con-
nection, it should be blocked off or connected to a separate line, which has an open end se-
cured above the level of the overflow tank.
The overflow tank itself must be open to allow decompression and attached above the fuel
tank, for example on one of the Nassau Panel brackets.
1. Slide the rubber carburettor connector over the inlet manifold, so it snaps into the grove
of the manifold, and attach it with a hose clamp.
2. Push the carburettor into the connector, so it snaps as well, and attach it with another
hose clamp.
3. Connect the fuel tank connector, which has the line on the backside, with the front
brass connector of the fuel pump.
4. Cut this line and install an in-line fuel filter (making sure it is clear from moving parts
and the ground).
5. Connect the fuel pump with the carburettor.
6. Connect the fuel tank with the overflow tank.
7. Connect the line of the (black, round) vacuum actuator with the nozzle at the inlet of the
carburettor.
Since the beginning of 2010 we have started using a new rectangular fuel pump instead of
the round Mikuni fuel pump. The advantage of this pump is that it has an internal pressure
limiter. Therefore it is no longer necessary to install a return to the fuel tank, and the needle
valve of the carburettor has better performance.
Note that the carburettors have now been adjusted to operate with the new fuel pump, so
they may not necessarily work properly with the Mikuni pump.
! The fuel lines must be made from fuel-resistant rubber.
! Attach the fuel lines to your kart using tie wraps or tape, making sure they are not
touching the exhaust, the engine, moving parts or the ground. Check that tie wraps
cannot move in case the kart should hit the ground.
fuel
tank
fuel pump
overflow
tank
Bing
carburettor
open
overflow
pipes
in-line
fuel filter
pipe for 3rd connector
ambient air
vacuum
actuator
carburettor

© Aixro GmbH / Woelfle Engineering GmbH 7/23
! Ensure that the fuel lines are not restricted by the attachment (kinks or sharp bends),
as this can damage the engine.
4.4. Throttle Cable
1. Loosen the nut of the elbow section at the top of the carburettor, so its direction can be
adjusted.
2. Lay an external throttle cable from the elbow to the throttle cable adjuster of your kart
and cut it to the correct length, so the throttle cable is not distorted (too long) or kinked
(too short).
3. Check the ends of the external cable making sure they are round and have no sharp
edges.
4. Pull the throttle cable through the external cable and the cable adjuster until it reaches
the elbow section and the cable adjuster.
5. Align the elbow to the external cable and secure the position by re-tightening the nut on
the carburettor.
6. Attach the outside throttle cable to your kart using tape or tie wraps, so that it is clear
from any moving parts and the ground.
7. Attach the throttle cable to the throttle pedal using a (twin screw) cable clamp.
8. Check the adjustment of the throttle cable and the throttle pedal. At idle position the
cable must be slightly loose while the slide of the carburettor remains at its lowest posi-
tion. At full throttle the carburettor inlet should be fully open, and the throttle pedal
should reach the limit screw of the chassis.
9. Tighten down the throttle cable clamp, the counter nuts and the pedal limit screws.
10. Attach the air filter to the flange of the carburettor and secure it with a hose clamp.
11. Avoid leaving a long open end of throttle cable behind the cable clamp. If the open end
is longer than 30mm, you should secure it. If your front bumper bar has a hole, you can
put the open end into the hole and attach it with tape. It is also possible to attach it to
the throttle cable with some small tie wraps or a fuel line, which you put around the
throttle cable before attaching it to the throttle pedal.
! Check the throttle cable for smooth operation. A sticking cable may result in injuries
or engine damage.
! Check that tie wraps used to attach the throttle cable to the chassis will not move if
the kart hits the ground. Otherwise the throttle cable can get stuck while driving. In
case of doubt it is better to use tape.
4.5. Exhaust
The attachment of the exhaust is similar to direct drive 100cc or KF-engines. It is attached in
an exhaust cradle and secured with springs.
1. Bolt the exhaust header to the engine with a gasket in between. Use 3 M8 nuts tight-
ened to 25Nm.
2. Attach the silencer to the header. Hold it horizontally and without tension. This is the
correct position of the exhaust if the chain tension (=engine position) is set correctly.
3. Adjust the exhaust cradle to suit the silencer position.
4. Lay the silencer in the cradle and attach it to the manifold using the springs provided.
5. Attach the exhaust to the cradle using standard exhaust springs.
! If the exhaust is not attached without strain or tension this may cause cracks of the
exhaust or manifold. Therefore you should also check the exhaust attachment when
you change the gearing or the position of the engine.
Depending on the design of the attachment it may be useful to use a thick plate with two
holes as an adapter for the exhaust cradle. This allows adjusting the position of the cradle in
driving direction. The height of the cradle can be adjusted with additional spacers.

© Aixro GmbH / Woelfle Engineering GmbH 8/23
If the exhaust is attached without strain or tension, the rubber underneath the cradle can be
removed. If not, it should at least be replaced by a strong spring, as the rubber will not with-
stand the heat from the exhaust.
If you should not have an exhaust gasket, you can just bolt the exhaust header directly to the
engine.
4.6. Electrics
From 2011 The Aixro XR50 is equipped with a PVL ignition, which includes some additional
features for onboard starting. Even when equipped with the onboard starter the engine will
start easily with an external starter.
4.6.1. External Starter
To start the engine with an external starter, use a 22mm socket on the clutch nut. The clutch
nut should be easily accessible through the bodywork, so the starter can be removed easily
after starting the engine.
1. Connect the ignition wires as shown on the diagramme below.
2. Attach the CDI box. Typically the best position is on the back of the seat. The CDI box
should not be too close to the engine or the exhaust.
3. Mount the stop button / kill switch, so it is easily visible for the driver. The steering
wheel is the best location. If it should not be possible to attach the switch to the steer-
ing wheel, you should drill a hole (Ø 15mm) in the Nassau Panel (within easy reach of
the driver) and attach the switch there.
4. Cover the wires you do not need and attach them with cable ties.
5. Drill or cut a sufficiently wide (long) hole in the side pod, and deburr it. Keep in mind
that the engine position varies depending on the gearing and chain length.
! Make sure the wires cannot wear or make contact with the ground and open ends are
protected. Otherwise it may happen that you cannot start or stop the engine.

© Aixro GmbH / Woelfle Engineering GmbH 9/23
4.6.2. Onboard Starter
If your engine is equipped with an onboard starter, you need a battery with a compatible bat-
tery tray and cables. Use a maintenance-free (MF type) lead-acid battery (no gel) with min.
7,2Ah and temporary 100A. Though the ignition has an integrated charging function, make
sure the battery is always charged sufficiently.
1. Connect the ignition wires as shown on the diagramme below.
2. Mount the battery in an appropriate position.
3. Run the cables along the chassis, securing them so they cannot wear or hit the ground.
Make sure the cables cannot make any electrical contact with the chassis.
4. Attach the CDI box. Typically the best position is on the back of the seat. The CDI box
should not be too close to the engine or the exhaust.
5. Mount the stop button / kill switch, so it is easily visible for the driver. The steering
wheel is the best location. If it should not be possible to attach the switch to the steer-
ing wheel, you should drill a hole (Ø 15mm) in the Nassau Panel (within easy reach of
the driver) and attach the switch there.
Use sufficiently big cables for the conductive circuit between battery, relay and starter motor
(10mm² / AWG8). 1.5mm² / AWG16 cables are sufficient for the control circuits.
! A shortcut between the battery terminals can destroy the battery or cause explosion of
the battery.
! To avoid short circuits during transportation you should always disconnect the posi-
tive terminal (+) from the battery when you stop your kart.