Would you like to upgrade your impulse powered Kalkhoff with a better/stronger motor?


New Member
I have a 2014/2015 Kalkhoff with a broken impulse 1 motor. Although getting an expensive new motor from Kalkhoff is an option, I don't think it is a good idea, considering the well-known issues with this motor (and also impulse 2). I am thinking of modifying the frame so that a better motor can be added, while keeping the same battery. I would make this by hand if I would do it for myself only, but if there is a demand for a bolt-on kit, I can come with a more elegant solution. This will require designing, machining, welding, etc and addition of a strong Chinese motor so that the product is a motor that can be simply bolted on. New controls will be added on the handlebar (while keeping the same battery).

I was wondering how many old Kalkhoffs are out there with a bad motor and if anyone is interested in purchasing a kit. How much would you spend on making your Kalkhoff bike work or is it not worth fixing it. I think these are well-built bikes with a poorly designed motor. I have read some posts about riders asking if it is possible to upgrade using a Bosch motor but I think it is not straightforward, plus it is a more expensive solution. Please correct me if I am mistaken.

Also, do you know if the bolt pattern on the frame was different for impulse 2? Local bike shop said impulse 2 cannot be installed on the frame with impulse 1 but I am not sure about that. I am in the San Francisco Bay Area.

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Active Member
I would not bother replacing the Impulse 1 for the Impulse 2 even if it does fit. It is a horribly unreliable motor.
I did get a new motor for my Impulse 2 bike and it broke, but now I have 2 so I can hot swap them when they inevitably go wrong I do not know the issues you were having, but mine always ended up sounding broken, at that point I will swap and change internal motor bearings which solves the problem for a while.
One time I lost drive totaly and it sounded like a maraca one of the bearings had litrally shattered inside, and the drive was gone due to the worm gear not being in contact with the spindle, there was no visable gear damage so new bearings and putting it back in place mended it.
If you are thinking about going for chinese mid drive. I am not sure retrofitting a different motor and electronics to it is the most cost effective idea.
And sticking to your original battery will restrict you to 36 volt systems.
Battery's are actually quite cheap when not made for a certain bike.
For example my Focus with Impulse 36volt battery will cost £900 to replace.
My 48volt battery for the bafang costs £250 and it has the same samsung cells found in the £1000 main brand replacement batt's.

I can not help thinking that you would be better off either picking up spares to keep that bike going, or selling it as a project bike or as spares, then going down the Bafang BBSxx type of route where you can get nearly any donor bike and fit it.
Or if you want to maintain torque sensing then the Ultra or M600 but this does need to have a specific frame.
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New Member
Thanks TomW, I agree with most of your points. Yes, I had thought about a Chinese mid drive, by installing a pair of plates that are machined and assembled with a bottom bracket that would allow me to use such a mid drive. I thought about this project mainly because I spent so much money on the bike, have two almost new batteries but is is very difficult to find used motor here. Also the frame, brakes, etc are of good quality. I disassembled the motor completely, the spindle was in very bad shape with a lot of corrosion, and the wires broke off. It has a coil based torque sensor in the spindle which was also damaged. If I can find a spindle, I could repair the motor. I occasionally find motors or parts in the German ebay but most of them refuse to ship it to the US. Unfortunately here in the US it is very difficult to find a used impulse motor. But you have a point regarding limiting myself to a 36V battery.


New Member
Will the Bafang 1000w motor fit on the kahlkoff, is that a possibility? Has anyone done this?