Dick,

Most twins exhibit differences between cylinders as far as operating temps go, this is mostly due to fuel distribution variation between cylinders and cooling differences between cylinders. If a person monitors cylinder temp versus engine speed (under load like running the engine on a dyno) and makes sure that both cylinders are getting equal cooling you will see that the temps differ from one cylinder to the other changes as you go through the RPM range, this is almost 100% because of fuel/air distribution changes due to engine speed causing first one then the other cylinder to get a bit more fuel mixture. This is refering to multi cylinder engines with single carburetors and common crankcase.

The above assumes that the exhaust system is independent for both cylinders and is the same physically.

The cause of this is that the crankshaft turns one way in the crankcase and it's slight "pumping" effect changes with RPM, that and the pulse effect of the intake charge sometimes is aided and sometimes opposed to some degree by the crank pumping energy pulses), the net result is a change in which cylinder gets a bit more charge than the other depending on engine speed.

Almost any multi-cylinder engine that uses carburetors and non symmetrical intake systems will exhibit this characteristic to some degree or other.

Bill Krueger