ah...a knock eh?...not often a good sign <_< I think i kinda know what you mean...it's noticeable but not horendous...like a sort of feedback through the pedal?
This is Guy's K12 website http://www.micrak12.com/ (I'm sure he won't mind it being pimped out a bit
)
If you click on the last full stop . ...of the homepage you will download a PDF K12_micra_service_manual...not sure which section/s will help but it's a handy thing to have for sure 
I think i may be the only K12 owner who's wiper linkage or motor hasn't packed up at all yet, just lucky i guess, had a blade split but that's about it 
(Mine's a 55 plate with 75K on the clock)
I think the only bad luck i've had with her was last winter the OS headlamp bulb went...and i had to change it in the dark *facepalm*
...not fun in daylight..let alone by torchlight...my dad helped as usual though...but i have smaller hands and had to do the actual fitting part
*Is so proud* 