I had been doing some thinking about the ignition switch failures on FJRs. This thread seems like a good place to post my "findings".
I think it is clear that there are (at least) two failure modes of our ignition switches.
Failure Mode 1 are those that fail due to poor contact (due to dirt, grime, etc) within the switches. This failure mode seems to be the less frequent one and spans all models, both generations. It may be precipitated by injection of various lubricants into the tumbler mechanism, which may run down and contaminate the electrical switch contacts. This is failure mode described earlier in this thread by Barabus.
Failure mode 2 are the ones where one of the 2 large wires (red or brown) comes unsoldered inside the switch. This failure mode seems to be primarily limited to 2nd generation FJRs. This is the failure mode documented nicely
here by DailyCommuter.
This failure mode seems to be the more epidemic one. It appears to be related to some sort of manufacturing problem in the wire attachment compounded by the design of having the majority of the bikes electric current flowing through the switches contacts.
The part numbers for the FJR ignition switches have varied twice during the FJR run.
The '03's have a switch p/n 5JW-82501-10-00
The '04's and '05's have p/n 5JW-82501-20-00
The '06's and '07's have p/n 5PS-82501-10-00
Yamaha doesn't have online fiche for '08s up for some reason.
The fact that the first three digits change is likely due to the generation change. But the change from -10 to -20 and then back to -10 makes me think that these parts are not exactly the same, or at least not procured from the switch manufacturer in the same lots. This may help explain why the melting solder syndrome seems limited to the 2nd gens.