SK3 motor bell and shaft loose do I fix it?

Thanks for your help in advance. Check out the video and you can see the bell of this motor is loose and wiggly. I think it is the source of some new vibrations and loss of torque. Does anyone know what I need to do to fix it? I want to get it fixed before any major problems

My first guess would be that you either broke the c-clip on the shaft and need to replace it or reposition it back into position. Most likely though, you need to take the motor apart and replace your bearings.

Cool …hopefully a simple fix! I’ll pull it apart tomorrow and post up what I find. I’m not sure what the typical life of a motor is but I have probably put about 300 miles on it so far.

My guess is also worn out bearings. Like really worn out. NJK are good motor bearings. Made in Japan. You can find some on eBay. As long as the magnets weren’t hitting the stator, you should be fine by just replacing the bearings. You can use a drift punch and hammer to remove the old bearings but you really need a small press or a C-clamp to install new ones. They should be a press fit. Don’t hammer the new bearings in cuz you might damage them in the process

To avoid getting this too soon you might wanna check your belt tension not too thight or too loose as well as makinh sure the alignment is perfect. Another tips is to get your belt position as close as possible to the motor mount to avoid torsional side load.

This happened to my sk3. Remove the motor and take a look at the 4 Allen mounting bolts on the part of the motor that doesn’t rotate. Most likely they are loose

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Thanks everyone for all the input. I took a look at the motor just now and @Alex was the diognostic winner!!! The screws had wiggled loose and all I had to do was tighten those up. I also added a little thread lock too. Everything is super secure now. Check out the image for reference.

Thanks Again!!


Got here late :slight_smile: But that is the only weak spot of the sk3, those screw get loose, red loctite fix that really good.

To remove the bearings you’ll need to use one if this

To burn the loctite without damaging the motor.

Loctite won’t always help - these screws also break quite easily. See:

When using Loctite the screws has to be tightened firm but not over torque. The Loctite it is what is going to keep the screw in place not the mechanical force. :wink:

Good to know! Might as well add Loctite to these black bolts while I have my drive-train disassembled.

Anyone ever have problems with the setscrews on the opposite side of the axle coming loose?

with breaking I meant what happened to me: the screw can not hold the force applied to the motor (for example with a tight belt) and breaks. Had nothing to do with tightening it. They are cheap and weak screws and can be upgraded to some real steel ones that withstand much more.

My motor hasn’t given me any more problems. The screws have stayed secure. I probably have approximately 700 miles on the motor so far😄

Oh yea this is what happened to 2 of my sk3’s but I was too late and already had a broken screw!

I was able to fix one and replaced with different m3 screws and lots of loctite. hope it survives!

The other still has a screw broken off inside, any tips to get it out?

Use a dremel tool with cut off disk to grind a slot on the end of the broken screw and then just use a flat head screwdriver to remove it. Be sure to mask off the rest of The motor so you won’t get metal shavings in there.

try this…works perfectly and is very very cheap…i have never had this tool fail me.


The 2 method above are effective ways to tackle this problem, just make sure no debris get in the windings or magnets :wink: