I'm either getting senile or the tensioner extension can improve.
When I bought my 2nd S40 a year ago, the first thing I did was pop off the side cover and measure the tensioner, I remember 18mm.
Today, I did it again and it's 15.7 mm.  Possible?

probably right, maybe I have a note somewhere.

You might have a tight spot in your cam chain?

That's true even if you add cold oil.

Went back through my notes when I bought the bike, noted everything EXCEPT tensioner extension ! Now corrected!

Yes ,  removed the small pawl spring so it doesn't engage ,at 19000 miles , after extending the plunger , still running original factory chain ,bike is now just over 34,000 miles  . I did have a bit of a hiccup early this spring ,as I have been going in to check it's progress every 5000 miles and was hearing some unusual ticking at idle speed ,but not above idle ,I opened it up to find the small snap ring missing an the base of the tensioner trying to slide off the stock mounting bolt (about halfway - as far as it could ) causing the guide to slightly misalign .(the a cause of the ticking).
          I have no idea why the snap ring came off ,it could be because my tensioner moves every time the motor temperature cycles ( and the reason I see little to no chain stretch) or because it was damaged by removal and reuse (it was original) is anyone's guess.
           Being " MacGyver", I removed the Bolt (Suzuki's term) that the tensioner is mounted to, and simply replaced it with a 8M x 50mm bolt with 3 -8mm nuts (used as the larger base against the inner case) ,it exactly matching the stock bolt's profile . now the body of the tensioner is trapped between a nut and the hex head of the bolt . the Suzuki bolt and snap ring joining the pawl spring in retirement.
           While I don't care if any members follow me down the path of removing the pawl spring , I do think the bolt replacement to be a better way to go, could be used by anyone ,an could remove the chance of  snap ring  failure.