I keep hearing a clunking sound coming from the chain area. I've had mine for about 3500 miles. I've removed the sprocket cover and cleaned out all the gunk and build-up. I've taken it to the shop twice and had it adjusted. Clunking goes away for about 3 days, then comes back. I've cleaned and lube the chain approximately every 500-700mi. And again the clunking comes back within a couple days. I read a thread saying that the chain might be binding. Wouldn't a trained mechanic notice that? So do I need a chain replacement?? Thanks for any help you guys can give!