My ryker over the last few weeks has become loud at start up only to quiet down when the engine warmed up after a minute or two. I check the service manual and it said that as part of the 6000 mile service you should tighten the exhaust connections. I didn't do that at the time and now I have 11,900 miles. So, I took off the heat shield by the exhaust manifold and sure enough the bolts holding the manifold on to the engine block were all easy to snug up (i.e. somewhat loose). I snugged them up and the problem is solved. Thought this might help others who experienced the same thing.