I've got a Craftsman 917.273080 with 46 in mower deck that has started wobbling/vibrating as soon as the electric clutch is engaged. I thought it was out of balance blades but I replaced them and it still wobbles. I've also replaced all idler pulleys. There is no obvious reason for this wobble, everything seems tight. The drive belt and center idler pulley are jumping around like crazy making the whole deck shake. I can mow with it but it sounds and feels like the deck is going to come apart it is vibrating so bad. What's causing my problem.
Could be a few things. Bad bearing in one of the mandrels, idler pulley has a flat spot on it, belt missing a chunk, bent/way out of balance blade...or if you hit something REALLY hard, a bad/bent spindle shaft. Carefully check all of the above.
Blades are new with only a few hours on them and in good shape. Belt is in good shape. I thought it was one of the idler pulleys and decided to replace them all, they are in new condition, but I will double check for a flat spot. No bent spindle, and all bearings seem to be good but how would I know for sure? Everything seems tight, no wobble in any individual bearing or pulley, all blades turn freely by hand. The spring on the idler pulley seems ok but it is old and might have lost some of it's tension, allowing that idler to move more than it should. Could that be it?
Motor runs good and smooth. I thought it might be in the clutch but it is working fine.