Slight Knocking

Ok, Im new here so not sure if this belongs here, I got a new set of tyres this morning, took it out to break them in and everything was fine (apart from a few scares with the new rubber), anyway, after about 100k I feel and hear a slight knocking comming from the back of the bike (if feels like its just behind and under my left peg), it only happens when Im accelerating from a stop or a very low speed and stops once i hit about 20kph, if I stay below that speed the knocking will go on, I brought it back to the shop and they had a look, messed around with the chain for a bit, the tension seems fine and sent me on my way, the knocking is still there, ive had a look and cant see anything loose
 
Does anyone have any idea

if it's in the rear left, it's probbly the chain - your never going to make it perfectly silent, if you ever took off your helmet you will hear the son of a B. make sure you clean it and lube the chain.. Also if your talking about knockin, are you using high octane?(just in case)
 
 

cheers, I think the fuel is 92 (could be wrong though, its the standard stuff over here), the sound was definitly not coming from the engine, I had a look at it a few minutes ago and I think the chain could be rubbing off the stand, I havnt got any paddock stands to check it but ill get 1 of the lads to hold it up on monday, it sounds like something is hitting the lower fairing and the faster the take off the louder the knock

    probably the chain hitting the swingarm

think your right with that 1, was just out with it, had it up and was easily able to slap the chain against the swingarm, so do I have to get my wallet out again or is there life in it, theres about 1mm left in it