Slight knocking noise while pedalling

[Ron Burgundy]

Should I be concerned with a slight "Knocking" noise that really sounds like it is coming from my rear hub "Smart Pie" that is only present when I am pedaling? Not noticed when using the motor without pedalling. I tried testing the bike upside down and heard it very lightly, but intermittently and difficult to reproduce without pedal resistance.

[Bikemad]

It is probably nothing to worry about, but here are some possible causes of noises coming from the back wheel while pedalling:

• The freewheel will produce a noticeable clonk each time the slack is taken up as tension is placed on the chain.
• If you're in the highest gear, the pins in the chain links may rub slightly against the chainstay if there is insufficient clearance
• If a new freewheel has been fitted with a badly stretched used chain this can result in an unusual noise from the chain/sprocket area while pedalling
• If the derailleur is not correctly adjusted to line up with the sprockets it will produce noises as the chain continually tries to ride up/down onto to the adjacent gear

However, if the noise is coming from the front chainwheel/bottom bracket area, it could be a loose pedal crank or the bottom bracket bearings themselves are loose or worn.

Alan
 

[Ron Burgundy]

I thought it was the bottom bracket bearing at first because it is hard to pinpoint it while riding. It is not any of the other suggestions you offered. I figured if it was the motor that it would be constant under power or pedaling. I guess if it is the motor it will progress to more noticeable problems before my year warranty is expired. I just dredd having to deal with a warranty problem because I will have to dismantle the majority of my install and be without a bike. 

Thanks for the suggestions in any case.