1991 Honda ST1100 manual just for grins:
Coolant change every two years. Inspection for leaks/cracks/ect. every 8000mi.
Spark plugs every 8000 miles. And that's a carb bike.
I don't know what's needed to get at the radiator cap.
If it can be reached with minimum access, pull the cap and check for corrosion under the radi cap. May show it was never changed from first owner. As far as my take on corrosion, it is better it's running than sitting for 30yrs (ST) and eating out, plus cracking radiator hose mounts.
That too means to empty the reserve container. As far as thinking squeezing hoses while push the air out, it may help if you see it move at the filler neck. But I found that it will suck at the reserve tank, and lower it a few rounds before it levels off.
I'd keep an eye on that because it will take a good 80mi round trip or two to suck what it needs out of the reserve. Check when cold.
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