I took a heat gun to the front and rear header at the exhaust port. The front read approx 160 deg F and the rear was approx 230 deg F. This was done at idle. The bike idles and runs excellent. Should I be concerned or is this typical for the rear cylinder to run so much hotter?

 

Was this done just soon after start-up or did you ride it around a little bit first then shoot it?

 

Just look at the engine. The front cylinder is open to cool, fresh air on 3 sides. The rear is boxed in. And when riding, the only air that the rear cylinder gets is the hot air off of the front cylinder.

 

Adding to Buffalolake's entry, the front exhaust port is the first thing the ambient air hits thus offering the most cooling while the rear exhaust port and exhaust pipe are confined in what may well be dead air space offering the least cooling. Do you know exactly what your heat gun actually measured? With a flashlight you can see the beam, but with a heat gun the sensing area is invisible. Might the front measurement have been of the heat shield rather than the bare pipe while the rear measurement might have been the hot pipe itself?

Harleys have been built this way for a long time. If the difference were important, some changes would have been made.

 

I satisfied my curiosity today. I rode with three friends today and when we stopped, I took out my laser temperature sensor and shot all four bikes at the header pipe about an inch from the flange. All read approx 50 degrees hotter at the rear cylinder. The other bikes were a 12 road king with VH dresser duals and 4" rounds, a 14 street glide with VH power duals and high outputs, a 15 road glide completely stock. So I feel all is good.