Follow this guide for how to change the umbilical on your bike. Note that this is the general procedure - some bikes you may need to perform additional steps and other bikes you may not need to perform these.
This guide will refer to two ends of the umbilical - the "Motor/Controller end" and the "Handlebar end" - consult the image below for an explanation on which end is which (note that the "Motor/controller" end on your umbilical may look slightly different but the "Handlebar" end always looks very similar to this).
- Wire Snips
- A "fishing line" - this can be: bike brake cable, bike shifter cable, twine, a thick guitar string
- 2.5mm Allen Key - bike with BBS02/BBSHD motor
- Phillips Screwdriver - bike with Bafang Ultra Motor
Remove your bike battery and discharge any excess electricity from the system by turning on the display with no batteries on the bike. Leave your bike battery disconnected throughout this process.
On a bike with a mid-drive motor, you will need to open up the motor cavity - see the following images for which screws you need to remove to do this
On bikes with a rear hub motor, you do not need to do this - except on the Kutty. On this bike, fold the bike open and undo the four screws pictured below. Then remove the plastic cover so you can access the motor controller.
Unplug the display, brake sensors and throttle on the bike. Take care when unplugging these wires - wiggle the connectors as shown on this page if you are having trouble disconnecting them.
Next, unplug the end of the umbilical connection to the bike's controller. If you are unsure which cord is the umbilical and you have the replacement cord find the connection that matches the size and shape of your replacement. If you do not have a replacement cord to look at you have two options:
- Unplug the largest connector coming from the motor - see picture below. Generally, the umbilical has the largest plug going into the motor.
- Trace the old umbilical cord down to where it enters the bike. Take note of how thick the cord is and it's flexibility. Then you can find a plug going on to the motor which is similarly thick.
The next step is to prepare the line for the removal and installation of the new umbilical. On the "Motor/Controller End" of the umbilical tape on one end of your "fishing line" (Note: do not use actual fishing line for this - use one of the types of line mentioned at the beginning of this guide).
Tape the "fishing line" onto the umbilical at multiple points with enough tape so that the "fishing line" will not come loose while pulling. Also, ensure you don't use too much tape! Too much tape will enlarge the plug diameter too much so it won't be able to enter the tight internal cavities in the bike.
Ensure any zip ties holding the umbilical to any other wires are snipped off so it is loose.
Pull out the old umbilical, pulling it from the "Handlebar End". Slowly pull, you may need to wiggle the "Motor/Controller End" so it can enter holes in the frame. Make sure to pull gently so nothing is damaged throughout this process and the "fishing line" does not come undone.
Now you will have the old umbilical removed but the fishing line will be lined up through the bike frame - see the image in Step 6 for an illustration of this. This is very important!
Now you will have the "Motor/Controller End" of the old umbilical removed from the headtube of the bike. Remove the tape connecting the "Motor/Controller" end of the old umbilical to the "fishing line". You will now have the "fishing line" running through the bike where the umbilical was previously running - see the image below as per how the "fishing line" will be run through the bike internally.
From here on forward you will be using your new/replacement umbilical - put the old umbilical cord off to the side.
Make note of the labels at each end of the fishing line in the image below - these will be important in the next few steps.
Now connect the "Motor/controller" end of your new umbilical to the "Headtube End" of your fishing line which will be coming out from the head-tube of your bike. Make sure these are connected strong and securely - we recommend taping about 4-6 inches of the fishing line and umbilical together in multiple locations - see image below.
Grab the "pulling end" of the fishing line and gently start pulling on it. This will move the "Motor/controller end" of the new umbilical back to where it needs to plug into. The "Motor/controller end" of the new umbilical may need to be guided into and out of holes on the bike frame depending on the size.
Take a slow and steady approach to this step - if something is not moving well try and find where that is occurring and nudge the part so you can continue pulling it. You do not want the fishing line to come undone from the bike at any time during this process - if this comes undone the installation will be exponentially more difficult.
At the end of this step, you should have the umbilical running through the inside of the bike. The "Motor/Controller end" will be at the location where it can be plugged back into the appropriate plug. The "Handlebar End" will be able to be plugged into the throttle, display and brake sensors on the bike handlebars.
Plug in all the connections on the umbilical. When plugging everything back in make sure the arrows on each plug are lined up!
Put the battery back in and power on your bike. Your bike should turn on and function correctly. If so put the motor cover back on your bike if applicable, redo any zip-ties or conduit you removed, and enjoy your bike.
If you are having trouble, please submit a support ticket using the same email you placed your order under. Please note in the ticket your Biktrix order number, the trouble you are experiencing and include photos of the issue.