S50/S51 Installation Manual for Simson S50
Please Keep Your Packaging To conserve resources in case you need to return the kit.
Prerequisites
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Included in the Kit
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Required Tools
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Before You Begin the Conversion
The purpose of the conversion kit is to modify the above-mentioned Simson models in accordance with this assembly manual and to operate them on public roads as described in the user manual. Please understand that this conversion kit was developed based on the original state of the specified Simson models. For vehicles that have non-original components, or whose parts were altered due to accidents, wear, or intentional modifications, we cannot guarantee that the kit will function correctly or can be safely installed. If you are unsure about your vehicle, feel free to contact us.
This document, “Conversion Kit SR24 - SR50, SR80 - Assembly and Operating Manual,” is provided by Second Ride GmbH and serves as a supplement to the original manufacturer's user manual. Both documents are to be used together, where information regarding the combustion engine can be disregarded.
Please read this document thoroughly before starting the conversion and before your first ride. It contains warnings, safety instructions, tips, emergency procedures, and other important notes regarding your vehicle. Ignoring the instructions may lead to injury, danger to life, or reduced vehicle performance. Pay close attention to all warnings, especially those concerning high voltage areas. Proper installation and operation of the kit can only be guaranteed if all instructions are followed.
Please note: The onboard battery, transmission oil, and fuel-oil mixture must not be disposed of in household waste, sewage, or nature. Inform yourself on the correct disposal procedures. Old batteries may contain harmful substances but also valuable resources such as iron, zinc, manganese, and nickel that can be recycled. Please return the seat battery to us after use. To ensure safe transport, we recommend using the original packaging. Always contact us before returning anything.
Some fluids used in vehicles (battery acid, coolant, brake fluid, fuel, windshield washer fluid, etc.) are toxic and must not be inhaled, swallowed, or allowed to contact open wounds. Always follow the instructions on the labels and comply with local regulations.
All technical information and descriptions were accurate at the time of publication. However, since continuous improvement is a core goal, we reserve the right to make changes to the product at any time. If you notice any errors or omissions in this document, please report them in our Discord channel (see footer).
Disassembly
Before starting disassembly, disconnect the vehicle battery to avoid short circuits.
1. Engine Connections
Start by disconnecting all electrical and mechanical connections to the engine. Ensure the fuel valve is turned off and detach the fuel hose from the carburetor. Drain the remaining fuel into a suitable container (e.g., fuel canister). Loosen the clamp on the intake boot and remove it from the carburetor. Unscrew the throttle (2) and choke (1) cables from the carburetor, detach the clutch cable from its bracket on the engine block (5), and unscrew the speedometer cable from its mount (6). Also remove the spark plug cap (3) and ground cable from the engine block. Remove the left side cover to unplug and remove the cables from the alternator.
2.Exhaust
Now only the exhaust should be attached to the engine. This is attached to the engine with a large nut (4), which can be removed with a pipe wrench or a hook wrench.
Tip
If the manifold nut won't come off, you can use an old slotted screwdriver and a hammer (preferably made of rubber or wood) to knock it into the notches in the manifold nut and loosen it.
The other attachment of the exhaust is at the rear in the form of a pipe clamp. This can be opened by removing the screw. You can remove the exhaust strut (7) at the same time. To do this, simply remove the screw at the top of the rear suspension strut, remove the exhaust strut and screw the suspension strut back onto the frame top rail and the top rail support strut.
3. Chain
Before the engine can be removed, the chain must be removed from the drive sprocket. First remove the alternator cover from the engine. Then loosen both the nut on the rear axle on the right and the quick-release axle on the left. A few turns are sufficient here, as the rear wheel only needs to be moved. You can now screw the small nuts of the chain tensioner all the way back to the end of the thread. It should now be possible to move the rear wheel forwards.
Tip
If the moped is jacked up on the main stand, you can now make the rear wheel float by lifting it by the frame upper belt and kicking the rear wheel with your foot so that it comes 1-2 cm forward.
Now it's time to lift the greasy chain off the drive sprocket. We have included disposable gloves in the package for this purpose.
4. Engine
The motor is now ready to be removed. It is screwed into the motor bearing plates (10) with two long M8 screws. It can be fiddly to lift the motor out. Assistance from a second person can be very helpful at this stage. Loosen the nuts and try to pull the screws out of the holes. It helps to lift the motor slightly. When both bolts are out, the engine should usually still be hanging in the bearing by itself. By lifting the motor now, you can remove it from the bearing. Congratulations! Your Simson is no longer an internal combustion vehicle.
Interesting to know
Karl Clauss Dietel, chief developer of the S50, told us in an e-mail that he had deliberately designed the moped to be so open. This would make it easier to change the drive if better drives became available thanks to new technologies. Thank you for your foresight! Prof. Dietel died on 02.01.2022. He had a decisive influence on product design in the East - whether it was cars, mopeds or radios. For this he was awarded the highest German design prize.
5. Handlebar attachments
On the handlebars, you can now remove the left hand lever and the clutch and starter bowden cable.
6. Seat
You should now remove the original seat so that you can fit our new seat straight away. This is attached to the top frame rail with three screws. The first one is at the front and can be removed from the left-hand side with a screwdriver. The other two are at the rear above the luggage rack. Et voila! Your moped is now waiting for its electric conversion kit!
Fitting the conversion kit
Only M4, M5, M6 and M8 screws are used when fitting the conversion kit. You should use the following tightening torques to ensure that the individual parts are held and tightened as intended:
M4: 2.9 Nm
M5: 5.7 Nm
M6: 9.8 Nm
M8: 24 Nm
1. Drive module mounting
The drive module is mounted on the vehicle in the same way as the original engine. Here, too, you should get help from another person. Lift the drive module and guide it between the engine mounting plates (10). The M8x100 hexagon head screw supplied is for the upper bore and the M8x90 hexagon head screw is for the lower bore. Using a ratchet with extension piece and 13 mm socket and a 13 mm open-end wrench for countering, tighten both bolts properly with the supplied M8 nuts.
Tip
If there was a snag when lifting the motor out of the bracket, then it is likely that inserting the drive module will also be difficult again. you have the following options to simplify assembly:
➜ Check whether the inner distance at the height of the lower hole is greater than or equal to 71 mm. If this is not the case, you will make installation easier if you widen the plates beforehand. To do this, first loosen the carriage bolt at the bottom of the retaining plates (11). Insert a threaded rod (M8 or smaller)
through one of the lower holes, attach a washer, two nuts and another washer, and then insert the threaded rod through the other lower hole. Now you can use the two nuts to widen the plates until they are 71-73 mm apart when relaxed.
After installing the drive module, always check that all 4 screws of the adapter block (9) are sufficiently tight on both the vehicle side and the engine side.
2. Chain
Now remove the chain guard from the drive module by loosening the three M4 screws and put everything aside for later. It's time for the gloves again! If you have an S50 (does not apply to S51) and have already fitted a 420 chain, you can continue to use this if you wish. You can tell if it is a 420 chain by measuring the width at the outermost points of a link. The 420 chain is 6.35 mm wide on the inside. The original Simson chain is 5.2 mm wide on the inside. If you decide to install the supplied chain, find the chain lock on the installed chain and open it. To do this, simply turn the floating rear wheel until the chain link with the chain lock appears. The chain lock can be opened with pointed pliers or a flat-blade screwdriver. Caution: Do not simply pull the chain out of the chain tube once you have opened it. You can use the old chain to easily fit the new chain. Connect the new chain to the new chain lock at one end of the old chain and now pull on the other end of the old chain until the chain lock reappears. Now open the chain lock again, place the chain over the drive sprocket of the drive module and close it again.Now you can pull the rear wheel back again and turn the chain tensioner nuts forwards for a rough pre-adjustment. Now start the fine adjustment with the right-hand chain tensioner: Turn the chain tensioner nut forwards until the chain only has 2 cm play up and down in the tube. You can feel this by pressing the chain tube together at the thinnest point between your thumb and index finger and making an up/down movement.
Once you are happy with the chain tension, you can now turn your attention to the other chain tensioner. Use this chain tensioner to adjust the so-called track of the vehicle. Sounds more complicated than it is. Just make sure that both wheels are in line. You can use a long straight board for this or simply squat three steps behind the moped and aim at the front wheel with one eye over the rear wheel.
If you are satisfied with the chain tension, you can now turn your attention to the other chain tensioner. Use this chain tensioner to adjust the so-called track of the vehicle. Sounds more complicated than it is. Just make sure that both wheels are in line. You can use a long straight board for this or simply squat three steps behind the moped and aim at the front wheel with one eye over the rear wheel.
Now check the chain tension again and correct it if necessary. If both chain tensioners are now correctly adjusted, you can tighten the rear axle and nut again. Now you just need to screw our chain guard back on.
3. Fittings
Now screw the speedometer cable to the chain guard you have just fitted. The plastic thread for this is in the same place as on the previously dismantled combustion engine. Your original speedometer (16) will now simply continue to work.
Warning
Due to the use of the DUO speedometer gearbox, the displayed speed is approx. 9% higher than the actual speed. If you are driving at 60 km/h, the speedometer will show almost 66 km/h.
The dashboard unit consisting of the ignition lock (14) and button (15) is attached to the front left M6 screw on the handlebar support. The charge level indicator (13) should first be screwed to the mounting plate and the rectangular plug from the ignition lock plugged in at the rear. The cardboard box of the charge level indicator contains washers and nuts for fastening to the plate. The mounting plate can then be attached to the left-hand shock absorber screw in the same way as the speedometer. Now plug the black connector coming from the ignition lock into the charge level indicator. You can lead the long cable from the ignition lock along the frame under the tank into the heart box. A cable with a matching plug comes out from the underside of the drive module. Guide it into the heart box and connect the plugs there. There are arrows on both plugs indicating the correct orientation for plugging them together. Securely fasten the cables to the frame using the cable ties supplied. Make sure that the cable is not pulled when the steering wheel is turned fully in both directions, or that it even hinders steering.
4. Throttle cable
If you have an N1 carburetor, you can now screw the throttle cable together with the piston and carburetor cover to the Bowden cable sensor. If you had a different type of carburetor on the combustion engine, the carburetor cover and piston will not fit and you will have to replace them. There are good explanatory videos on this on the Youtube channel Simson Werkstatt
The notch in which the carburetor needle is mounted, or whether it is completely missing, no longer plays a role in the function of the Bowden cable sensor.
Turn the carburetor piston (19) as shown in the picture so that the groove (29) points towards the rear tire. There is a pin on the same side of the cylinder (20) that you can feel with your finger. The carburetor piston must then be inserted into the cylinder so that the groove is guided over the pin. You can then screw the carburetor cover (18) onto the cylinder. Make sure that the cover is screwed on until there is no longer a slot between the cover and the stop.
Now it is time to adjust the throttle cable. There is an adjusting screw for this under the rubber cover (17). If the throttle grip is turned all the way forward, i.e. no throttle is applied, there should be no play on the throttle cable housing. You can reduce the play by unscrewing the screw. Later, when the battery is connected, you can check your setting:
If you press the ignition switch and nothing happens when you accelerate, then the screw was turned out too far. If it is possible to accelerate and there is no play on the cover, then the setting is exactly right. You don't need to worry that the upper stop could be wrong and you will have reduced maximum power, as the stop at full throttle is always the cover, which is always in the same place every time the throttle cable is adjusted.
Warning
Please be sure to refit the rubber cover (17) on the carburetor cover. Otherwise the sensor may be damaged in the rain.
Make sure that your throttle cable and throttle twist grip have the lowest possible frictional resistance. The throttle grip should snap back completely from the maximum open position using the spring force alone. If this is not the case, it helps to remove the throttle twist grip, clean and re-grease it and/or replace the Bowden cable. It is also possible that the rubber of the throttle twist grip is rubbing against the clamping piece. It helps to push the rubber on the dismantled throttle grip tube outwards. You can find video instructions for throttle twist grip maintenance on the Youtube channel 2Radgeber
5. Electrics
You can tie the thick orange cable up to the front mount using cable ties. In general, you should avoid cables rubbing against sharp edges or corners.
the on-board power supply (lights and horn) is supplied by a voltage converter in the drive module. A black cable with a white plug comes out from under the drive module. Feed this into the heart box in the same way as the dashboard cable. We have supplied you with a wiring harness with a matching white plug at one end and several flat receptacles and a ring cable lug at the other ends. Now connect the white 2-pin plugs. You can attach the black wire to the earth collection point in the heart box. Now connect the red wires of the second ride cable to the ignition lock at the following contacts:
59, 59B, 30, unlabeled triple plug
Incidentally, you no longer need to use a fuse, as the power supply automatically switches off in the event of a short circuit until the short circuit is removed again.
Under this link you will find the wiring diagram suitable for your moped. It shows which components can be removed and where you have to connect the red cables. You don't have to worry about doing anything wrong. Our drive module has short-circuit protection, so the light will not come on until you have rectified the fault.
If your vehicle is still equipped with 6V electrics, you will need to replace all bulbs and the flasher unit with 12V components.
Interesting to know
The 12V bulbs are significantly brighter than the 6V versions and the horn is also louder with 12V. After the conversion you will be safer on the road.
Now you can set the original ignition switch to the position with the headlight or “II” symbol (the third in the clockwise direction).
Finally, you need to connect our brake contact cable. This cable tells the drive module whether you are actuating the rear wheel brake (or the front wheel brake if you also have a brake contact there). As long as the brake is applied, it is no longer possible to accelerate. The package contains an 80 cm long black cable with a white plug housing at one end and a flat plug sleeve (22) at the other. Connect the white plug to the white plug on the underside of the drive module and run the cable along the swing arm to the brake contact (24) on the rear wheel. Remove the original brake contact cable (23) there, plug ours on and connect the original one to the extra lug that comes off our cable.
The rear mount (28) is screwed to the other two attachment points of the original seat bench.
Now place the seat bench on it once as a test so that the front mount and the tank move to the correct position. To do this, first hook the seat into the rear mount (28) and then lower the front end of the seat onto the front mount (26). You can check whether the seat is positioned correctly by turning the lock cylinder of the seat with the key and pushing it in. If the locking cylinder cannot be pushed in until it engages, the seat has not yet been pushed deep enough onto the mount. The front mount and the tank are now correctly aligned. Unlock the seat again, remove it again in the opposite order to that in which it was fitted and tighten the screws of the front mount (25) (27).
Warning
The seat does not have a retaining strap for a passenger. It is therefore necessary that you have fitted the support bracket (8) to the luggage rack so that your vehicle can continue to be used for pillion riding.
Now you can mount the seat back on the vehicle for your first functional test. Just don't forget this time to plug the orange cable into the corresponding plug in the seat bench after hooking it into the rear.