Recently bought an '88 XR600 and it seems to run fine most of the time however it doesn't idle very smoothly. After running at idle for a while it will cough and die without warning (easy to restart). Have tried increasing the idle speed which will help a bit but doesn't stop the problem all together. I've noticed carbon build up near exhaust so is obviously running a bit rich. I am new to the XR600 game so if anyone knows of any common reasons the old girl might be doing this I'd really appreciate the help..... Thanks.