fat bike mid drive


Active Member
Well i took my KHS500 fat bike to the local bike shop yesterday to have the bottom bracket removed. This to check it to see if the bike is a candidate for a BBSHD 1000 w mid drive motor. And it is. These motors work best on bikes with a JIS/BSA threaded bottom bracket. There are adapters made for a couple of other styles as well. And the KHS500 4 season fat bike is a candidate. It,s bottom bracket is 100mm but i will be ordering the 120 mm to cover some possible interference due to the chainstay. The vendor will send a few spacers with the kit and sometime in the next week the kit will be ordered. So I will be the proud owner of 2 electric bikes, 1 BIONX road bike and a mid drive fatbike. I used to ride enduro motorcycles and trials so the fat bike is going to make a great dirt bike.
Well I ordered a 1000 watt BBSHD for my fat bike and it should be here in a few days. Hopefully all will be well.
Motor and battery came today. Its a lizard style case pretty common style and I had concerns it might not fit in the frame but thankfully it does. I will put fresh batteries in the old digital camera and take a few shots of the process. But it will be sitting untouched for a few days yet while I catch up on tasks around home.
Got the motor installed. Had to use my dremel to remove some of the inside of the bottom bracket in order to slide the drive shaft through the bottom bracket. Roshan from Biktrix provided the kit and he recommended I use a 120mm HD . With the KHS 500 it might have been possible to use a 100 mm HD. The reason I say this is on the left side where the threaded shaft sticks through the bottom bracket I had to use 2 approx 1/4" shims in order to have threads visible to be able to apply the locknut while the right or sprocket side needed two thin shims adding up to about 1/8" in order to give clearance for the chainstay. Took me a good part of the day removing a little material at a time, finally managed to slide the motor shaft through the bottom bracket. I don,t think any photos are in order, the ones i downloaded are too big for the site, not sure how to downsize them.
Last edited:
@Hugh, open the images you shot with a simple picture editing program, like Paint (usually comes preloaded on most computers). Then select 'edit image' you will see some options to crop or trim the picture and resize it. I usually look at the image size as 'pixels' and set the width or height (whichever looks bigger) to 400-600 pixels and that will be just the right size to display in the Forum area. Once you do the resize, save that altered image with a different name if you want to preserve your original image.

Then you can upload your images here. Do one at full size and choose 'Thumbnail' for any others. Then anyone can click on the smaller thumbnail images to see the full image; this helps to save space and keep the post tidy! Feel free to start a conversation with me if you need more help.
Well a couple updates while it's still fresh in my mind. It seemed like a good idea to include a gear sensor. You remove about an 1 1/2" from the rear derailleur cable sheath after removing the inner cable. The gear sensor is then spliced into the derailleur cable. Sounds pretty straightforward only I wasn't sure how to pull the inner cable out till you tube came to the rescue. Just remove a small plastic screw from the shifter assembly on the bars and once the cable has been unbolted at the back just pull the inner cable out far enough to remove the small piece of the derailleur sheath. Pushing it back through proved impossible. Besides the cable fraying it turned out KHS uses a slightly thicker inner cable that would not go into the gear sensor. A quick trip to the local bike shop solved that. The bike now has the battery, motor, new chain ring, pedals and gear sensor and speed sensor installed. Still need to put the ebike rated chain on and figure out the hydraulic brake cutouts.
The KMC ebike rated chain came in and was installed, the chain line is just about perfect, by having a couple different thickness of shims available it was possible to install the motor with a couple millimeters clearance between the motor and the chainstay. A smaller 42 tooth sprocket was purchased and installed. Then a small glitch, got the battery charged but the unit will not turn on. The kit was purchased from Roshan at Biktrix and I have been in contact with him and I am positive he will be able to help. He has responded to my questions in a timely manner and I would not hesitate to recommend him and his business. He is located in Saskatchewan and I am in the next province over, Manitoba, I decided to use a Canadian company to avoid customs, etc. Once I get it running I will add the brake sensors and take it for a spin and post an outside picture
It,s alive. The problem was a bad connection in what I believe is called an Anderson connector. Roshan is sending me a new battery cradle but looking through the shipping box, noticed their was another set of power wires included so I cut the original leads off the battery cradle and soldered on the other leads and voila it worked. I have the gear sensor installed and it works great, momentarily cutting power when shifting so shifts are smooth. And yesterday the brake sensors were mounted and tested. I cut 2 pieces 1 1/2" long by about 3/8" wide of some light gauge tin, bent part of it to wrap around the brake lever, and used epoxy to mount the pieces to the brake levers and also the small magnets that trigger the sensor. The sensors come with some tape that allow them to be test fastened, once they were in the right spot a zip tie was used to hold them in place and then epoxy was applied. i used Permatex cold steel epoxy, it gives you 5 minutes time before stating to set. Then a short ride down the back lane to test it. What an amazing difference even just using power level one. Today it is just above freezing so a better longer test ride is in order. I will take my camera along to get a couple pictures in the natural light and see about posting them.
ebike 006 (500x375).jpg
This picture shows the speed sensor mounted to the chainstay and on the far side is the gear sensor which works great, allows nice smooth shifts by cutting the motor briefly when changing gears. Before I reached this location I was riding along a river on a foot path that was about 2 feet wide with soft snow about 2 feet deep on either side. needless to say I slid off the packed down portion of the trail many times. Once i remembered my old trials riding tip which was watch where you want the wheel to go not where you don,t want it to go things got a lot better.
Last edited: