How do you judge the wear and if a replacement is neeeded on the duplex primary chain fitted to a Sherpa.

AFAIK, as long as they stay in oil, they run virtually forever.

If you really want to check it, I guess the same way you'd check a drive chain.

Try to pull it back away from the sprocket.

If you expose more than about half a tooth, the chain is shot.

Fit a primary chain tensioner, if you do not already have one.

FWIW I replaced a duplex primary chain on a B40 after 20 years (no expense spared)

Compared the old one with the Renolds replacement, not a mm of a differance.

Has always been run in TQF.

Good to know the duplex primary chains last & last, thank you for the replies.