Cam Chain worn out at 22000 km(14000 mls)???

[Bobmech]

I have a 2001 XT600E DJ02 4PT with 22000 km(14000 mls) on the clock and the cam chain is worn out/noisy.
The auto tensioner has half of the teeth exposed(8 out of 16).
It is only audible between 3200 rpm and 4000 rpm on the highway & that's with a loud straight-through muffler !!
My first thought, being the 4th owner, was that previously the speedo had been disconnected. But the mileage done by each previous owner seems consistent. Also, the cam chain guides, camshaft, valve stem ends & clutch plates, etc all show virtually no wear, & it uses no oil.
The first 7000 km were done in Japan which would typically include a lot of idling in traffic, which may be a factor?
.
Is it normal for the cam chain to be noisy at this mileage ?? :confused1:
.
Bob