Tapping noise coming from left side of the motor (KZ550)

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The inner pipe coming out on the left hand side of the motor runs colder than the others. I found this out when I sprayed the pipes with high temp black paint. The others baked the paint dry almost instantly, but the pipe in question took almost 5 seconds.
The right side exhaust gas comes out warmer than the left side when the bike first starts up in the morning. It doesn't seem to run crappy or anything, but it does have a tapping noise on the left side of the motor between 1900-3000 rpm. Once the bike has been ridden for a bit & the oil warms up, the tapping almost goes alway entirely. It hasn't let me set yet and I've put a good amount of miles on it already (coming up on a 1000 in 4 weeks time). Of course the motor does have 32,000 miles on it.

Any clues/ideas what it might be before my tear down on the motor this winter?