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Craftsman 917.287121 keeps throwing drive belt

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Re: Craftsman 917.287121 keeps throwing drive belt

Postby 38racing » Sun Mar 31, 2019 10:51 pm

dart451 wrote:I thought I'd close this post with this. I did buy an 89" belt and installed it. That fixed the problem! Now it moves perfectly...

did you measure the 89 belt to see what is actual was? Seems funny that you have to be an inch shorter that the size sears calls for. At least being hydrostatic you won't have a disengagement issue.
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Re: Craftsman 917.287121 keeps throwing drive belt

Postby KE4AVB » Mon Apr 01, 2019 7:19 am

Personally I still think the V-idlers are worn and allowing the belt to bottom out in the v-grooves. I have seen a lot these plastic pulleys worn out. What I look for is shiny bottoms on the v-groove indicating belt slippage. Also you can where the sides are worn into a step fashion groove.
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Re: Craftsman 917.287121 keeps throwing drive belt

Postby dart451 » Wed Apr 03, 2019 4:26 pm

I did measure the belts. The 90" belt measured at 89.5" believe it or not! And the new belt measured at 89". So, KE4AVB, what bothered me about that theory my friend was that the plastic pulleys all had a flat at the bottom of the "V"...same as the flat at the bottom of the belt at it's narrowest point. I figured that even if the pulley sides wore, it would never get any lower than when it hits the flat bottom and appeared as though it was there already. Unfortunately, I didn't order a new plastic pulley to see the difference in the old pulley and new pulley. If (when) I get the tractor back to me, I will order a pulley just to ease my curiosity. I can mic the pulleys to see what type of wear it has.
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Re: Craftsman 917.287121 keeps throwing drive belt

Postby KE4AVB » Wed Apr 03, 2019 5:11 pm

When the pulley is new the v-belt never rides at the bottom of groove unless the v-belt itself is worn. When the v-belt does rides at the bottom of the v groove it slips on the pulley creating a shiny bottom plus it over speeds the bearing as the pulley will be turned by inner circumference of the pulley as it is driven by the bottomed out belt instead the higher normal outer circumference position. I change a lot of these pulleys because of this. Sometimes I get lucky and can install a metal version of the same size if I can change out the stand off bushing.
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Re: Craftsman 917.287121 keeps throwing drive belt

Postby dart451 » Thu Apr 04, 2019 8:06 am

Thank you KE4AVB, I will change the pulleys next time I get the tractor back...
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