Have you, or any of the other M3W owners done the Bleazey mod to easily access the coupler "dampers" for inspection and/or replacement?
The Bleazey mod is very popular in the UK and pretty much regarded as a "must have" by those of us who use our M3Ws for touring. There's a group who regularly do 5,000 or more miles a year and mine is just rolling over 40,000 miles in 4 years.
If you haven't already then join the MTWC Touring Group Facebook page to see how usable these wee beasties can be:
https://www.facebook.com/groups/511022087505443
