The drive belt that propels the machine keeps coming off the idler pulley. It appears that the idler pulley is positioned we below the other two pulleys. Is there a way to move the idler pulley up so it aligns with the others.

Check To See If The Pulley Has A Lot Of Slap, Or Slack In It Where It Has The Bolt Through It, The Bearings May Be Going Bad In The Pulley. I Don't Really Know How Much Lower You Are Talking About , A lot To Me Maybe 1/4" Where To You It May Be 1 1/2" , Just Can't Tell Without More Info. Check To See If The Pulley Mounting Arm Appears To Be Bent.
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Thanks, Mowerman2468