rear brake squeal but indicator still in "usable..

Many years ago, I made the bike I had at the time with rear brake drums "Self Cleaning". I took new brake shoes and using a hacksaw, cut two diagonal slots across the shoe material equal distance from the end.

I then used a hand file to bevel the cut slots to provide an exit for brake shoe material when the system was squeezed. I never had any trouble in noise or loss of braking action.

my 77 kz650 also squeaks in back even though the indicator is only shows 50% wear. I just ignore it. I know the brakes arent dirty because i just cleaned the dust out and it didn't fix anything. Probably just cheap pads.

Most aftermarket shoes work OK on the rear and rarely squeel, but last set I put on was Vesra and the pads were too big diameter slightly so it was impossible to get any play to set the correct free play in the pedal. Also don't rely on the range indicator, it can be rotated anywhere on the splines, may show good and you're metal on metal, so best to look at the shoes, not the indicator.