First of all, I am going to give my bike to the shop this week. So I like to know how severe it is (as I have to ride my bike to the shop) and it's also good to know how much money this is going to cost me to fix! Since last week Saturday my bike does a clear, loud 'klonk' when turning the back wheel. It did it the first time while I pushed it, but I wasn't able to reproduce it enough to make other people believe that there was actually something wrong. It hasn't really been showing until a week later. But even then it was not often enough (I couldn't make the sound on purpose) so that I wasn't able to ask others to have a listen. That day I rode her a bit on rural roads and after that she started doing it quite often. I had to ride her again today, and now the status quo is as follows: When the back wheel is being turned - doesn't matter what gear, whether under load or not (does it when turning it by hand when up on the paddock stand) there is this very loud 'klack'. You can feel that klack. It can happen more or less frequent, I don't think that it depends on how fast I turn the wheel. It happens when it's being turned in either direction (I believe more often when going forwards). It doesn't always happen at the same point. Sometimes it happens more frequent, then it might not occur for a few turns. I can't really see anything jumping around. I have the feeling that the sound originates from just to the right of the axis - that would be where the brake is. I had originally thought it might be the chain, as it sounds similar to that, but I can't see the chain jumping around or anything. Right now it is really worrying me as it started doing that A LOT since my last trip. The bike in question is a 1989 Honda Spada. On the day she did that sound the first time, I had something done to her front, but not her rear. Some person did though grab a screw driver and wriggle the chain up and down quite a bit (in order to show me the chain slack) - I wouldn't have thought that that would cause any issues. Any pointers are appreciated, would be nice to know what's going on before giving her away!