Assessing cam and primary chain wear

[matchlessman]

I have an '81 CBX with about 70,xxx miles on it. A couple of years ago I read in a Classic Bike interview of a British CBX guru that maintained that cam and primary chains should be renewed at 50,000 miles. Obviously I'm well past that point. Neither chain seems to be making any bad noises, in fact the engine is quite quiet mechanically, doesn't burn any oil to speak of and is generally well maintained.

What are owners' experiences with cam and primary chain wear? I'm not anxious to undertake a complete engine strip down to change these two chains unless there's a really good reason. Was the Brit expert assuming that an owner had ridden a bike really hard and not maintained it to suggest cam and primary chain replacement at what seems a low mileage?

Ken
Eastern Ontario