I know I should have done more research before posting but just so you know, there is a Goldwing whisperer in Florida who has probably seen it all. I understand he is very helpful and could possibly help in your decision making process going forward.
Just Wings, Tampa Florida. Greg is the contact person.
https://justwings.com/Yup, been seeing the Just Wings guy popping up in a LOT of searches. Just posted on the Goldwing Tech Talk on Facebook, need to e-mail Greg and also get on some of the Goldwing forums as well... I think I MIGHT have narrowed it down to something with the alternator, or (Hoping not!) the alternator drive gear. Evidently the ADG failing is common enough it's got an acronym, and the fix involves a total removal of the engine. Ugh.
Cut and paste of my post on Goldwing tech forum. Not trying to turn this into a GL1800 tech forum, but with as much cross pollination as there is between Valk people and GL1800 people figure this info might be at least a little valuable to other folks here...
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Howdy, got a perplexing issue...
Short version - 2008 GL1800 60k miles. I bought it less than a year ago, initially all was great. Took a short ride while on a long trip and it started making LOUD embarrassing noises. The noises would change as I shifted gears, sometimes louder, sometimes it'd go Goldwing quiet. Also, when first engaging the clutch handle it pulsates rather quickly, a vibration but more of an in and out pulsing.
The sound seems to decrease, but not 100% go away as the bike warms up, but the clutch handle pulsation doesn't change.
I recently came across the ADG issues on the GL1800s and that made me listen and the sound does seem to come from around the alternatorish area. I've listened to other ADG issues and those are more "clunky" than I'm hearing, mine is more of a smooth whine/whirr....
I'll try to get a stethoscope and listen closer to the alternator, but before I get there figured I'd check the amassed wisdom and experience here. I took a video of what's going on, as usual the sounds aren't 100% accurate, it sounds louder in person.
Any thoughts, ideas, suggestions? I've searched until the search results are starting to get blurred to me so figured it was time for a sanity check...
(And yeah, that's the short version, the long version involves this starting 1500 miles into a 5000 mile trip with one of my 11 year olds, having the bike shipped from Billings Montana to Dallas Texas, a local shop having the bike for a month and finally throwing their hands up in defeat, etc..... Not been fun. The irony being I bought the 'Wing 'cause I was getting worried my 1998 Valkyrie was getting too old to reliably take cross country anymore.... Heh.)
https://www.youtube.com/watch?v=CzKIclQdC7w