Debugging a Troy-Bilt sicklebar mower

With the Jari on the disabled list (burned up motor, leftside wheel, and shroud), I set to rehabilitating the 42″ Troy-Bilt sickle mower I bought last weekend.  It started right up when I bought it, but it had a damaged belt, which I thought was the reason it jumped off the pulley when I engaged the sickle bar.  So I bought a new belt (1/2″x35″, for future reference), put it on, and it fired up the cutterbar, but it too jumped the pulley as soon as I put it under load.  There were two little bent steel ‘keepers’ on either side that seemed designed to keep the belt on, but they only extended halfway down the axial depth of the pulley, so I thought maybe they were insufficient, and I made better ones out of scrap aluminum.  However, as soon as I started to cut grass, the belt jumped the pulley again, and my new keepers very effectively ripped the belt in two.

mower broken belt

 

At that point I suspected something more fundamental, and in looking carefully I noticed that the motor pulley was axially mis-aligned with the cutterbar pulley by about 3/8″.  Joshua and I puzzled on it for a bit, and we noticed that the pulley was held on the end of the shaft with a suspiciously non-factory-looking bolt and stack of washers.  To my surprise, the pulley was not frozen to the shaft, but rather moved easily once the set screws were released.  I tapped it up into alignment:

mower shaft

 

Given the retrofit bolt arrangement, I didn’t judge that the set screws were capable of holding the pulley in place, so I whipped out a spacer on the Bridgeport – didn’t have round tubing the right size, but 1″ thin-wall aluminum square tube fit over with a bit of encouragement (must be a 7/8″ shaft):

mower shaft with spacer

 

I Secured the pulley with the bolt and washer stack, reassembled using the old belt (not about to blow another brand-new $14 belt on this mower), fired up, and it cut nicely for about 100 yards.  It was too hot in the middle of the day to really put it through its paces, but I think we’re provisionally back in the sickle-bar mowing business.

The Troy-Bilt seems a little slower than the Jari, but has 10″ of extra width, so they probably will work at about the same rate.  It’s a wider, heavier machine with janky plastic catches on the levers for the tank-style independent steering clutches, and at first go I don’t like it quite as much, but I suspect I’ll get accustomed to it.  Still, since I think I have a spare engine that will fit the Jari in place of the burned-up unit, I think I’ll order a replacement wheel and try to put it back in service eventually, as limited spare time permits…

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