fluctuating speed on belt sander

[Tana]

My belt sander speed seems to fluctuate from slow to normal speed as well as not have much power when I use it. I use it mounted upside down. I thought it might be the sanding belt being too loose on the rollers but that wouldn't make the motor slow. I haven't pulled it apart yet but was hoping someone might point me in the right direction. It is a Ryobi CB76K (in Australia but made in China)

Thanks, Tana

[CW]

I would suspect brushes. Check/change them immediately. Failing to do so can destroy your motor.

[Tana]

thanks, i'm on to it. Cheers T