I have a bike, about 7 years old. Just bought it, used, when i pedal, sometimes, usually when in the top rear cog, the power does not engage right away. The cranks spin without resistance for about 1/4 rotation, and then something engages with a bit of a "thunk" noise, and then my pedal power works at the rear wheel.
The cranks/bottom bracket and chain are all new. I was wondering is this is a problem with my hub or cassette, should I have them replaced. What would I be looking at for cost, would it be better to buy the $100 wheelsets off ebay?