Ready to fit your own motor?
Our advice is that if you are not a competent home bike mechanic, don’t fit your own motor kit – get us to do it. However, if you know your way around a bottom bracket, then you should be fine.
You’re going to need to undertake the following jobs, and for each you will need some specialist tools. Read through our fitting guide below to check you have the right skills, confidence and tools to do the job yourself. In general, we feel that for most people our fitting service costs less than the tools you may need to purchase!
1. Remove the chain and front derailleur
Tools: Chain tool (none required if chain has quick link)
You will need to split and remove the chain if it goes through a front deralier. You may have a quick link which means the chain can be removed without tools, but in many cases you will need a chain tool. Some chains (Shimano for example) won’t allow you to simply push the pin back into the chain – you need a new, over sized pin. Others (11+ speed chains) will need a chain tool with a peening anvil. Having removed the chain, now remove the front derailleur.
2. Remove your pedal cranks and the bottom bracket
Tools: Bottom bracket socket and bar or bottom bracket tool, crank puller tool, penetrating fluid (if your bottom bracket is stuck), 8mm hex key or wrench (sometimes torx drive)
Remove the cranks using the hex drive and crank puller.
Then you need to remove the bottom bracket. This is the bit that stresses us. Bottom brackets have a habit of getting stuck. You’re going to probably need a breaker bar to shift them and a good spray of penetrating fluid. There have been cases where additional bench tools or techniques are required, but in most cases, the bottom bracket socket and breaker bar will do the job.
3. Fit the motor
Tools: Bafang fitting tool, Torquewrench or Blue Loctite Threadlock.
In most cases the motor slips into place. However, in a fair few, the inside of the frame may need a clean up with a round file. You may also have cable guides under the bottom bracket that are too big. These will need replacing with more streamlined ones.
Once the motor is in, it will need to add and tighten the lock wring and a further aluminium one over the top. Be aware – this lock ring requires a lot of Torque. Bafang recommend 60ft lbs. Other people believe it should be nearer 100ft lbs. If you do not tighten the inner ring enough – it will loosen. You could add locktite threadlock to it if you do not have a torquewrench, but make sure it is the ‘blue’ one so that it does not make it impossible to get off again.
4. Fit your components
Tools: Allen keys, small pozidrive/Phillips screwdriver. A Torx Pin / security driver is useful but not essential.
Once the motor is fitted, you can add in the chain wheel, cover, speed sensor, gear change sensor and plug in the main wiring harness. The accelerator and screen can be fitted to the handlebars. Make sure the accelerator is not mounted the wrong way up or water will get in and you’ll have a controller fault within a few months.
The speed sensor has a small magnet that needs attaching to your spokes. To do this, you need to use a small torx pin (security) driver. It is also possible to tighten with a small flat screwdriver.
The gear change sensor will require you to disconnect the gear cable and carefully push it through the sensor. On some bikes, the outer sheath will also require cutting, with a short length matching the length of the gear change sensor being disposed of.
5. Fit and connect the battery
Tools: Allen keys, insulation tape. Optional extras – soldering iron, rivnuts and rivnut tool, heatshrink,
In a perfect world, the battery simply screws to the bottle mounts using your allen key, and the socket fitted to the battery matches the plug fitted to the motor. However, in the real world, you may have a few stumbling blocks.
Often, the bottle mounts are in the wrong place, or they do not sufficiently support the heavy battery. Especially with off road use, batteries are subjected to a lot of bashing around. If that is the case, consider adding an additional rivnut. If you mount somewhere where there is no bottle cage mount, then rivnuts are the solution.
Connecting the motor to the battery may be easy if everything matches, but often it doesn’t. We tend to do a solder joint, which is sealing using silicon and heat shrink insulation. This makes a waterproof and long lasting joint.
6 Fit your brake sensors and tidy up.
Tools: Allen keys, wire cutters, small pliers, zip ties, strong glue (maybe)
If you have cable brakes, then simply use the replacement levers found in your motor box to replace the existing ones. If your existing brakes are integrated into the gears (often found in cheaper bikes), then you will either need to replace the gear changes as well, or use external hydraulic sensors on the existing brakes.
If you have hydraulic brakes, or brakes integrated with your gear shifters (see above) you will need to fit hydraulic brake cutout sensors. The magnet glues or sticks to the brake lever, and then a sensor sticks to the brake lever housing. When you pull the brake lever, the brake sensor detects this and cuts power to the motor. You will need to adjust these carefully. It’s very easy for them to completely cut power at all times (so you have a dead bike) or not at all.
You can then go all round your bike and tidy up using your cable ties, cutting off any excess with your wire cutters.