Re: radiator fans not turning on until 234 degrees '01 929
I have a couple ideas after reading this thread. My hunch is the coolant, rad cap, thermoswitch & fans, and maybe waterpump.
Make sure the cap is indeed good.
Do the 929's have an inspection hose for the water pump seal? Anyway, I'd inspect the waterpump too.
If there's any doubt about the history of the coolant, as important as it is, change it!
After you know the radiator is properly full of new coolant, empty the overflow bottle, and put the cap back on. Then burp the system. Let the bike cool completely: the radiator should be completely full, then check the overflow bottle. Add coolant to the level marks on the bottle.
When your bike is running, the overflow bottle should be less full, when the engine cold, more full. When you said it was full because it was hot, that's not how it should be. Air in the system could swell and push coolant to the overflow bottle and fill it up like you described.
I've tried Prestone, Dex Cool, and Engine Ice. All are free of silicates-that's important.
The Engine ice works best by an honest 5F degrees or so cooler than the others.
I'd inspect the thermoswitch for good contact, and the fan for overall condition. Shouldn't be any drag when you spin it by hand. Verify it's kicking on and off after your done burping.
I haven't been around bikes as long as some of the guys around here, but I haven't heard of thermoswitches failing. I'm sure they do, but I just haven't heard of it. I don't know how to test it, so I guess I'd replace it if you can isolate the problem to the fan Not kicking in at the right temp. 219-220
Keep a close eye on your engine oil or if your coolant turns a funny color since you got so hot the other day. I'd change that oil. Got pretty hot...