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BBSHD significant resistance when pedaling with motor off or not engaged

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    #16
    It is kinda annoying that no one ever said what the issue was. I have heard that the factory lubrication is a little hit and miss on these. Same thing with the bearings some are better than others and get decent lubrication at the bearing factory and some don't.

    The nylon gear and motor should not be turning if the motor isn't getting power. The whole reason its got a clutch in it is to act as an overrun so the motor doesn't end up slowing things down or turning into a generator which is good if you are expecting it and designed for it but very bad for systems like this that are not expecting it.

    Taking the cover off behind the chain ring isn't too big a job and if its not very old the gasket should be reusable. There is a bearing for the big gear that will stay in the cover. With that out you will be able to see if its got an issue by seeing how well it spins in the cover. If thats really dragging you found your problem. If its fine you can try turning the small gear which is the shaft that goes through the nylon gear. The directions are reversed on it so ccw should spin fairly free. Cw should engage the clutch which means gear will be trying to spin the motor. I don't think its a common failure to have the clutch stick but I suppose its possible.

    The nylon gear is on the other side and the motor part has to be removed to access it. I'm pretty sure to get the motor off you have to remove and disconnect the controller to get the 3 main motor wires loose from their seals.

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      #17
      Every time I've heard of this issue coming up and it being resolved (several times) it was always an issue with the overrunning clutch in the nylon gear

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      • 73Eldo
        73Eldo commented
        Editing a comment
        So new nylon gear? If its low miles pinion shaft should be fine but if you had this issue on a higher mileage unit maybe the shaft could be damaged too?

        I suppose you could get lucky with a clean and lube but given the cost of the gear its not likely that high a quality clutch bearing to begin with.

      #18
      Thank you very much 73Eldo and AZguy for your replies and info. I guess I will be opening up the motor and see if I can find anything. I have a couple of other items to take care of on the bike and need to source some Mobil 28 grease so will be a few days. I will post if I find anything (or also if I don't find anything!). I have been on a couple of rides and really like the BBSHD on my bike but it would be very nice if I can reduce this drag on the crank arms if possible.

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        #19
        In the meantime based on another suggestion I tried loosening the M33 nut on the non-drive side. I had it pretty tight after reading about cases of loose motor brackets allowing the motor to rotate due to torque. Surprisingly it made a difference on the amount of resistance at the pedal. Went from ~ 1 1/2 pounds of force needed down to about 1/2 pound. I don't understand this but perhaps I was causing some internal stresses and deformation on the motor housing with the tight M33 nut? In any case, I have reinstalled with a less tight nut but due to concerns of the motor rotating under torque I added a stress member that ties one of the mounting bracket bolts to the bike frame at the chainstay pivot sleeve bolt (see pic, this is a full suspension bike). The current amount of pedal resistance is much more acceptable to me but I may still open up the motor to see what I can see.

        Click image for larger version

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          #20
          I like your support bracket. Unless you are putting some extraordinary force on that nut I can't see that really making any different unless something is hitting on the other side somewhere other than right around the BB area. You want to at least be able to slide a sheet of paper between the gear case and any part of the frame. Is it maybe hitting that pivot bolt on the other side? If its hitting something I could then see it basically bending the tube a bit which would cause extra drag.

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            #21
            I have ~2mm clearance between the reduction gear housing and my chain stay and more clearance than that for everything else. The bottom bracket has never had any work done on it previously so no reason to suspect other than factory flat faces on both sides and therefore nice seating of the Bafang motor housing on it. I was surprised to find the crank resistance being reduced by just loosening the M33 nut. I did have it pretty tight due to concerns of motor bracket slippage due to torque and that motor mass bouncing up and down. This is a mountain bike so it will experience some "bumpy" trails. In any case, not having it so tight did make a big difference for my installation. I will probably not tear into the motor any further than just looking at the main gear and clutch and lubricating them. Waiting on delivery of the Mobil 28. If that doesn't help I can live with the ~ 1/2 pound of parasitic force needed on the pedal that I have now. I am glad that such an easy adjustment made such a difference for whatever mysterious reason it did. The only reason I can think of was slight deformation of the motor housing due to having the M33 nut so tight. Again, thanks for taking the time to respond and offering your suggestions.

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              #22
              Doesn't sound like there should have been anything to distort the housing then. What sort of tools were you using to tighten it? With the typical wrench and no extra levers I don't think you could get it too tight. If you had the socket and a long wrench or bar then sure I suppose you could get it too tight.

              Got a ride in yet? If not hopefully real soon?

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                #23
                I used the Bafang special wrench for tightening the nut but tapped it a few times w a rubber mallet for that last bit of tightening (sometimes I get carried away with the bigger hammer approach :) ). Went for about a 10 mile ride (this is before I loosened the nut) and everything is working very well. I am going to enjoy this kit and the extra freedom it brings. Can't help but put a smile on your face.

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                  #24
                  Strange. That doesn't seem excessive, maybe good n tight but not stupid tight. That's about what I did on all 3 of mine. I should go out and try and compare the drag on all of em and see if any are any different than another. I'm pretty sure other people have gone a lot tighter. Seems like I have either seen or heard of people with the socket and something like a 3' breaker bar which for sure could go tighter than a couple taps with a rubber mallet.

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                    #25
                    This thread is full of pop culture, Mr. Fusion, Nick Nolte, and Slim Pickens.

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