I noticed recently on my 1999 Honda ST1100 Pan European a small hole in the hollow section that links the two sides of the swingarm.
After removing the rear wheel and scraping bits away, I saw the hole became larger. I removed the swingarm with the intention of re-plating the hollow section, it’s what I do for a living so it wasn’t really a problem. When I cut away some of the corroded section I was horrified with what I saw inside. The whole inside of the nearside swingarm had totally rusted away. I have put a golf ball there to show you the size of the hole.
If this had rusted away on the inner section it could only mean the lower section of the nearside swingarm was paper-thin. I shuddered to think what could have happened if I had been touring two up with my wife with the bike fully loaded. Check your swingarm now!
After purchasing a new arm I noticed a slight recess on the offside that is in direct line of all the salt and muck that the rear wheel throws up. It has a small hole where the water is supposed to drain away, but it becomes clogged with mud allowing water to collect and break into the hollow section and rust away inside. I filled the new arm with waxoil.