A while back while doing a morning drive around checking cuts I noticed a 4 " area on outside of drum not getting cut ?I did Square the reel to drum to find out later that a drum bearing had let go .
Bearing replacement was easy and straight forward .
Invest in a bench plate . get the biggest one you can afford . Not used a lot but in this situation is the perfect tool for an accurate job .
26" mower just fits . I strap the front down to hold reel on 1/4 gauge bar .
Front face of bedknive should contact front of bar as in picture above . We are squaring the actual reel to the rear drum drives .
In this case the adjustments are made on the right hand drum belt side . Remove cover.
Loosen 4 bolts through gear openings . You may need a pry bar to have drum fully seat on bench plate before and during tightening bolts back up . There is a 10 mm spec tolerance for drum gap . Double check afterwards before reassembling .
While your already here you might as well check the drum belts . Mine are checked every oil change . Guys that tend to snap them on and off will usually snap the left drum belt .
Loosen back side of idler gear . By turning the front nut the camber in bolt will adjust the belt .
Belt should deflect 1/4" at 4 to 5 pounds pressure .