The thermostat primarily does two things, accelerate engine warm-up time and regulate minimum
From what I gather, the RC51 usually doesn't have much problem maintaining minimum temperature once warmed up.
What I'm interested in is regulating the maximum engine temp.
I would use the temp sensor I linked from ebay, or a similar design, to automatically activate the SPAL fan to keep the operating temp in the range I specify.
So it would be like the radiator fan switch mod, but automatic and set to maintain a temperature window of my choosing. That's why I am interested in seeing what the "best" temperature range is.
Just as with the case of the cold engine, it’s not terribly uncommon to find a coolant temperature map that becomes extremely rich once a certain high coolant temperature is reached. The additional fuel slows combustion, greatly lowering combustion chamber temperatures. The additional richness also cools the combustion chamber through evaporative cooling, as was mentioned in the section on cold running above. Honda is particularly fond of this strategy, which is prevalent on the RC-51.
Wade, A. (2004). Motorcycle fuel injection handbook. St. Paul, Minn.: Motorbooks International.
The way I understand it is that there is a lookup table that enriches the mixture beyond the normal fuel mapping dependent on coolant temperature. During startup, when the engine is coldest, more fuel is added. As it warms up, this is decreased until the ideal operating temperature is reached. This coolant temperature lookup table begins adding fuel again in addition to the normal fuel map, as the engine heats beyond its ideal operating temperature.
The article on rc51.org seems to say that it isn't quite as simple as I described above and that the ecu doesn't simply continue to enrich the mixture the hotter the engine gets. It implies that there might be "better" windows at an even higher temperature.
What I'm looking for is the RC-51s ideal operating temperature. The service manual states that the thermostat begins to open at 176-183° F and is fully open at 203° F. To me that means the ideal operating range is between those numbers... but perhaps not? That is what I'm looking for.