2000 Lawnboy 10525 with 3 speed gearbox - when drive engaged , belt " chatters " . Cable adjustment seems correct . When disengaged , nothing feels loose . Any suggestions ? Thanks BTW , this is my first Lawnboy , used a Toro with the Suzuki motor for 25 + years , got a tractor , and sold it . Ended up missing the 2 stroke , got good deal on two 10525 . Duraforce and Suzuki seem very different ( to me ) .