I have a little over 300,000 miles on three GL1100's 54,000 on a GL1200 what do you want to know? lol
I bought a 83 Interstate spring of 2019 with only 40,000 miles on it. Cosmetically like new and it ran but barely. New set of cambelts and lots of carb rebuild later it finally settled down and ran pretty well last summer but my Gas MPG is still not where it should be. I would pull all the brake calipers push the pistons out till the very edge of the seal is visible the scotch bright the pistons. EMGO makes acceptable master cylinder rebuild kits you can use honda accord cambelts you get at NAPA 250274. After cleaning the pistons and rebuilding the master cylinders I can easily lock up both wheels when braking.
The carbs are a little tougher to tackle. It seems Honda used a lot of od sized rubber in these and Generic parts often cause as many problems as they solve. I went through the arbs completely on my three previous GL1100's but none of them gave me as much trouble as this one, I mark it up to age (mine and the bikes!
) Progressive still offers shock upgrades for the 1100 but theya re somewhat generic in nature so I just added preload to the front, the back is sufficient for putting around.
Here is a site with lots of vintage wing info
https://www.goldwingfacts.com/