That would depend on the efficiency of the exhaust and the wrap. A non-contact thermometer would tell you approximately what you have. It varies, and double walled and/or chromed pipes don't give accurate numbers with the laser thermometers, so people usually target the flange at the head. The only way to know what would be ideal for your bike would to be running it on the dyno at steady state and monitoring the air-fuel ratio. Once the air-fuel ratio was stabilized for a minute or so (with fans operating to simulate going down the road) you could take a temp measurement and consider that to be the average desireable value, but there are too many variables for absolution. If you get into the indigo colors of oxides on the un-wrapped header, it's getting pretty warm, but that don't mean much. It's exhaust, and should be hot! Trouble is, a peak temp in that range can cause the oxides on your chrome, and it won't reflect your average values. There are cylinder head temperature systems out there that are basically a thermistor ring that goes around the base of the plug. Cylinder head temp is a better indicator of what you have going than exhaust header temperature, because it's a larger heat sink and is more thermally stable than the thin-walled pipe. Many aircraft have CHT and EGT gauges so you can keep and eye on both, but and aircraft engine deals with much higher thermal stress than any of us are likely to put on a motorcycle engine. Then again, I'm and information junkie, so knowing sounds like fun to figure out one of these days. My pipes on my SV650 have been pale yellow forever, and I've been happy with that. there is a patch of blue at the exit of the rear cylinder, but that area gets saturated by flow out of the head, so I don't worry about it, just like I don't worry about my blue elbows on my XS head pipes. My SV is water cooled though, so different beast.
