Paul, the original T-Bob (TB-1) had an automotive size t-stat. I went from a TB-1 to a TB-3 and, now, to a TB-2. The TB-2 and the TB-3 both have the Cheap Chinee Scooter t-stat.
These things are somewhat problematic as the quality control is, um, Cheap Chinee Scooter quality. That's why wattman ships two in every kit, I believe.
The first one I had in the TB-3 was absolutely wonky. Neither Bill nor I could figure out just what it was doing. The thing of it was that it acted perfectly normally in a pot of hot water on the stove but, in the bike, it acted like it was stuck open. Actually, it acted like it wasn't there. Or perhaps it was confused. The second one was fine and has been perfectly reliable for the past 15K miles or so. I have transferred it over to the TB-2 and mounted it exactly as I had it in the TB-3 with respect to its orientation to the incoming bypass line.
It will be interesting to see if the location of the T-stat has any bearing on the observed temperatures. I still have a temp sensor down near the radiator outlet where the bypass mixes with the radiator output. I haven't had a chance to wring it out yet and see what it does.
I'm going to Taos for a few days but I am taking the BMW, so I don't know when I might be able to see what it is doing. I might just take the KLR for a run up to Death Valley when I get back from Taos.
There probably was a difference between the TB-1 and TB-3; I don't remember the details. I think that would be attributable to having the TB-1 control the inlet temperature to the radiator while the TB-3 was controlling the radiator's outlet temperature. Both had 195°F T-stats.