Gen2/Motor Bearing Replacement
From Unofficial Zero Manual
This replaces the motor bearings on Gen2 Z-Force motors.
- C-clip pliers
- M10 tensioner
- Loctite 648
- Hub puller (to extract the bearings)
- Replacement bearings (front and rear are both 6006-2RS on an FX used below)
- In these instructions, the front of the motor is the left/shaft-side, and the rear of the motor is the right/encoder-side.
- Prepare a clean workspace, removing all debris and metal tools that you are not directly using.
Warning: The rotor magnets are so strong they rip tools out of your hand and they attract every single metal filing that might be near by.
- Remove the motor from the bike.
- Removed the belt pulley:
- Remove the M10 countersunk bolt.
- Put two thin pieces of metal under the pulley, and drive two M6x1? bolts into the two threaded holes of the pulley to lift the pulley off.
- Gently pry the front cover off.
- It will most likely be stuck on the rotor so you'll be lifting the rotor out of the housing with it.
- It is actually quite straighforward to pull apart, but requires a lot of force.
- You can built a little chair (width of the plate, you put it on the cooling wings) with an M10 tensioner.
- Then you bolt an M10 eye-bolt (or T-handle) on the pulley so you can pull on the shaft really hard (about 200lbs), and the rotor will pull out on the shaft along with the drive plate and bearings.
Warning: Once you have the shaft and rotor out, be careful as it is highly magnetic and you can get your fingers pinched quite easily on it.
- At that point, the rotor should be loose on the shaft.
- If you have to remove the rear bearing, remove the c-clip holding the rotor laminations on the shaft, use a marker or something to mark the front and back of the rotor and how it is aligned on the shaft because you are going to take it off.
- The end of the rotor on the back side is aluminum so do not press on it.
- It houses tiny magnets that the motor position sensor (encoder) reads; damage to this will ruin the rotor.
Warning: It is important that it goes on in the exact same direction, otherwise the motor could spin backwards.
- Once you have the rotor and the shaft labeled so you can get them back together exactly the same way, slide the rotor laminations off the shaft.
- Clean the shaft and the inside of the laminations.
- Apply a lot of loctite 648 on the shaft and lamniations, then slide them back together.
- Ensure that they go together the same way that they were before.
- Endure that the loctite 648 gets well-distributed between the shaft and the laminations to make a solid bond.
- Press the rotor out of the front cap
- The bearing is held into the cap by a retainer so the rotor is pressed from the bearing.
- Remove the front bearing retainer and press the bearing out of the cap.
- Put the c-clip back on, put the bearing back on (or put a new bearing on since removing a bearing without damaging it is quite hard, the front and rear bearings are both 6006-2RS).
Warning: When you put the new bearing on, make sure you just push on the inner race for the press fit, if you push on the outer race it will transfer the force through the balls and likely damage them.
- The bearing should be a press fit; if it slips on or off easily, you should glue it on with the loctite 648.
- Let the 648 cure for a few hours before putting the motor back together.
- To put the motor back together, just do the same thing you did to pull it apart, but opposite.
- Ensure that the wave-spring is still in the bottom of the bearing pocket at the bottom of the motor.
Warning: Be careful to not let the rotor slam back into place, that could damage the bearing
- Temporarily lining the inside of the stator with a plastic sheet can prevent damage to the stator and rotor.
- Make sure you control the rotor: use the little chair and unscrew the tensioner to let the magnetic forces pull it back in slowly.
- Once it is almost all the way in, the bearing will catch on the bearing pocket.
- At that point, it might take a little jiggling around and some force on the end of the shaft to get it to pop into place, then it could take a bit more force to get the drive-plate to re-engage with the stator case.
- Notes from Travis Kimbrell
- Pin G and pin H are the thermistor leads.
- Mine, at 70° F showed roughly 600 ohms (in case anyone wants to do any testing).
- Each bearing housing has a big rubber o-ring that seats the bearings nicely.
- I learned that the rear motor cap does not have to be removed to service the bearings.
- I wish I had known that because it would have saved a lot of time.
- The dealer charges over $1,500 to replace these motors when most of the time it's as simple as bad bearing which cost me $38 and a few hours of work!