Appears that very little actual rad fluid exists and the PO had used mainly water. Have done 4 runs and flushes through the rad and thermostat housing using distilled water with considerable rust found each time.
Now working on putting a few hours on it using "Peak"flush fluid. Hoping this will work but uncertain at this time.
Anyone with a similar experience and final success, or maybe this just needs to be thoroughly serviced by a speciality rad company?

 

Using the radiator flush will help some. The internals of your radiator may be heavily rusted. Ditto for the water pump vanes if they are steel. The flush should have chemicals in it to help disolve corrosion and rust. Some will leave a coating on the metals. Once the flush is done, you usually flush with distilled water. Then, use a good anti freeze compatible with aluminum. Don't forget to check your thermostat as well, it has steel in too.
If it continues to show rust, you can take to a radiator shop and have it boiled out and pressure checked.

Hope it turns out ok.

 

+1 If you have to take your radiator to a shop for cleaning, it shoulnd't be too expensive. But you might as well replace the tstat, and water pump if it comes to that. I know around here radiator shops will void a warranty quick for not doing the rest. Plus its cheap enough to justify the loss in time/money to have to redo the boil out if something breaks loose. I'm not sure if they make one for bike, but I know my shop has a heated radiator flush machine we use for getting metal shavings etc. out of radiators, trans coolers, oil coolers. Ill have to look but I'm pretty sure the adapter will fit. That could be a possibility to "hot" flush your whole cooling system, water jackets included. May be worth checking into.