Looked at the Factory Service Manual and reviewed the damper shaft, spring, damper lifter, and damper cam. In my opinion none of those items will produce a clunk sound that can be heard while riding the motorcycle.
I am back to the U-Joint slamming against the inside of the swing arm. The ST1300 is a direct drive motorcycle so that when the clutch engages the power goes directly and immediately to the back wheel. Before it gets to the back wheel it has to go through the U-Joint. The force of that power could push a failing U-joint against the inside of the swing arm causing a clunk sound.
Here is a test to recreate the clunk sound to determine if it is the U-Joint. Have a friend that is an excellent rider sit on your ST1300 on the center stand, engine running, and holding down the rear brake firmly. Put a $20 stethoscope (available at an auto parts store) on the swing arm where the u-joint resides. Have your friend put the motorcycle in gear and slowly release the clutch to duplicate the power load of a start. Listen for the U-joint to see if it hits the inside of the swing arm. Repeat a few times to confirm. If you want to try this without a stethoscope you can put your hand or ear on the outer side of the swing arm directly above the U-joint.
Tried this with a friend who has worked as a motorcycle mechanic (at a Honda dealership) but has no ST wrenching experience. Used a stethoscope. He listened while I rode the bike. He heard nothing - and regardless of how I started the bike running in 1st I could not duplicate the noise. I tried it lightly dragging the brake, with the brakes full on, easy start and rev it up a bit and let the clutch out smartly. No difference, could not make it happen.
He listened w/ the engine off, manually rotating the wheel and compared it to his GoldWing. He said no difference in sound. Shock and swingarm are tight (no play). He was intrigued by the primary damper and said I should not be having ANY issues with the bike at 26k miles.
I paid a lot of attention to the noise on the ride to and from my friend's house (about 12 miles). I could get the noise intermittantly only in 1st. The noise happens when the clutch lever is almost fully released and the bike is just beginning to move - i.e. when the clutch is first loaded. Dealer mechanic said it was possible to gently release the clutch and get no noise and reliably get it with more power on the takeoff away from stopped.
Looked at the Factory Service Manual and reviewed the damper shaft, spring, damper lifter, and damper cam. In my opinion none of those items will produce a clunk sound that can be heard while riding the motorcycle.
I am back to the U-Joint slamming against the inside of the swing arm. The ST1300 is a direct drive motorcycle so that when the clutch engages the power goes directly and immediately to the back wheel. Before it gets to the back wheel it has to go through the U-Joint. The force of that power could push a failing U-joint against the inside of the swing arm causing a clunk sound.
Here is a test to recreate the clunk sound to determine if it is the U-Joint. Have a friend that is an excellent rider sit on your ST1300 on the center stand, engine running, and holding down the rear brake firmly. Put a $20 stethoscope (available at an auto parts store) on the swing arm where the u-joint resides. Have your friend put the motorcycle in gear and slowly release the clutch to duplicate the power load of a start. Listen for the U-joint to see if it hits the inside of the swing arm. Repeat a few times to confirm. If you want to try this without a stethoscope you can put your hand or ear on the outer side of the swing arm directly above the U-joint.
Be interesting so see if the sound is different with the bike on the center stand with the swing arm extended when the u-joint has more to do loaded and unloaded with the rear brake while running.
If it is the damper behind the clutch basket that's, I think, the 1st one posted on st-o.
fwiw the attachment URLs don't resolve for me.
Could be just an issue I'm having with MS Edge.
Again, I could not dupe the noise. Sorry about the URL's not working - I scanned the pages in the Shop Manual - go to clutch and a couple of pages past the pic of the clutch basket you will see the damper shaft, spring, etc.
