Hi mastertrophy,
I note your comment :
The dealer told me its very close to final adjustment..
Is it possible that it's the Tensioner blade and assembly that is worn,
rather than the chain itself ??

Examination and / or replacement of the Cam Chain is not even mentioned in the Service Schedule,
just to check the Valve timing, and to check and adjust Valve clearances every 20,000 miles,
so from that information alone, it would appear to be reasonable to expect that the chain
should last the life of the motorcycle, and certainly well beyond 40,000 miles.
IF it is accepted that chain wear at 40,000 miles is NOT normal,
then it makes sense to work out the cause, so that it doesn't happen again ! .....
If it HAS worn such that it needs replacing, then possible reasons could include :
Lack of lubrication
Incorrect assembly
Incorrectly machined Sprocket(s)
Faulty chain assembly or materials ( e.g. metal too soft / not hardened correctly )
Whatever the cause, if it were me, I would be contacting Triumph directly,
asking them to investigate, and to rectify the problem under warranty.
According to the Service Manual the procedure for checking chain wear is to :
Hang the chain wiith a 13Kg weight on it, and measure the distance
between 23 links of the chain - measuring between the centres of the link pins.
The maximum permissible specified length is 150.14mm
NOTE that this only checks for wear in the
length of the chain,
which should also be visually examined and checked for :
- Severe wear of any of the outer plates' contact-points
with the sprocket teeth, and other parts of the chain - Signs of stiffness or kinking.
If any of these are found then the camshaft chain should be replaced.
Cheers

