I have taken up bike commuting this year and am slowly learning my mechanics but this has me stumped and I'm hoping someone can help me out.
The problem: When pedaling I recently/sometimes get a kunka, kunka, kunka sound and vibration through my pedals to my feet.
1. It's intermittent
2. It starts for know reason but will consistently quit (more than 50% of the time) if I drive over a significant bump. But sometimes goes away on it's own without a bump.
3. It's loudest in the small chain ring and the 3rd gear of the rear cog; or the mid and large chain ring and 4th gear of the rear cog (7 on the cog). It gets significantly quieter the further you are away from these combination's.
4. Bike is Davinici Milano
5. Happens only if I pedal
6. Is not consistent through the pedal stoke but not random either. Meaning it doesn't happen at 2 o'clock and 8 o'clock every time. It's more like 2, 7, 12, 5. Sequential but by an odd number increment that I haven't figured out.
I suspect the crank bearings but it doesn't make sense to me that it would be louder in certain gearing then others.