Remove the seat. Remove the false tank. Disconnect the hose that goes to the coolant reserve reservoir. Get a container and place it in front of the radiator. Get your socket set and to the right of the oil filter cover is a bolt (10 or 12 mm I think) and loosen it. Make sure the bike hasn't been run.
Let it weep and flow out into the container. when done, open the radiator cap itsel (that's why you need to remove the false tank. Replace the bolt you removed and put in the flush. Run for 30 minutes after reaching temp. Let it cool down a couple of hours. Drain the radiator like you did the first time. Replace with clean water. Run for 10 minutes so it can circulate through the radiator. Cool down. Drain. Replace with anti-freeze.
Did mine two days ago. Did oil change and rear drive, too. No leaks and no extra parts left over! Win win.
It's also a good idea to test the switch before installing it again. I just held mine under a flame and you can hear a "click" to let you know it works as it turns on and off. Just wire brush it clean after. Also, make sure that when you put it back that the connector is snug on. For my 1200 the connector was difficult to attach. My fan kicks in after about the second bar on the dash btw. Hope the project went well!
Welcome. I see you are close by. Are you actually out riding in this heat?
I have never "flushed" a cooling system on either a bike or car with anything but distilled water. A guy I used to work with flushed his on a car, and all his core plugs started leaking. Had to pull the engine out to replace them (yes, I'm sure they were already pretty well corroded) but the engine was not overheating. I flushed my 1200 with distilled water. I put it in, ran the engine for awhile, drained it, and repeated that 3-4 times, until it came out perfectly clear. The main idea was to get all the old coolant out. If you use some kind of flushing chemical, which usually contains acid, I would do the same thing, flush it really good to get the stuff out before putting coolant back in.
I have the digital instrument cluster, and my fan comes on at 6 bars. In the summer, it never drops below 6 bars, and the fan just cuts on and off over and and over again.
I had some overheating problems with it a while back, which I now believe were caused by an air pocket trapped in the system. Filling it through the drain opening till it started coming out the radiator filler with a pressurized garden sprayer seems to have solved the problem.