make sure your belt is good, maybe try a new one, but first take a burgandy scotch bright to the sheaves and scrub them down to fresh aluminum, scrub from the inside to out leaving the little scratches for the belt to grip. take apart the secondary and do the same. then blow out the primary dust, note what weights are in it, check the rollers, wipe the sheaves clean with a little carb spray on clean paper towel, wipe with fresh towels until dry/clean, reassemble, fire up spin the track good, then check/adjust deflection.
Good time to check/adjust track tension/alignment too.
gotta make sure you start with clean slate before you mess with anything. stock helix is 48. works great imo.