What are the symptoms of a worn out S/C Belt tensioner spring?

Any Idea how to test one to check it's Tension? I'm guessing it's supposed to be XXft/lbs of pressure..

 

There must be a way of checking belt tension ??
But if your getting belt slip under load and yer belt is new why not just replace the idler.

I know I have plenty belt tension cos if yer not carefull that 1/2" long breaker bar will smack you in the chops if yer not carefull swapping belts.

When I changed to the Whipple from the Magnum I found I got less belt slip under full load but had this annoying squeak untill the motor got well hot then it would dissapear. Sounded like a dawn corus of birds
So I changed the belt but after a day or so it would start squeaking again.
Plenty of belt tension so this time I changed the belt over to run the other way and after running some 300 miles - no squeaking. - yet !

As for tension I guess if your unsure change the tension pulley, got to be cheap option for you guys but expensive for us in the UK

Maybe the works manual would shed some light on the issue ?

Good luck buddy.