i got a exmark lazer-z hp 52 deck 500 hrs on it the other day i had bolt to break on idle arm pulley that round housing were the bolt goes all the way under your deck bolt like maybe a 6 -inch bolt the housing also has a grease fitting on it . I put a new bolt in it it lasted about a week . i think housing and idle arm is all one piece . what could be my problem . i don't really know a lot about mechancial things thanks for your help.