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That there's worth fixin'
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Discussion Starter · #1 ·
I bought 1/2" BY 33" belts to replace the old ones. part nos. are A-31 or 4L-33. Got the size from the manual. The 33 inch belts are too short. I measured the outside of the old ones and they are 34". Anyone run into this before? Started wondering if maybe the pto pulleys are a different size than normal. Could the early tractors have used a different belt size. No model no. on this tractor but the motor dates to 72. Thanks for any help, Rick

 

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You are right!!! I bought the belt size listed in the manual. 33" is too short. I couldn't even get them around the PTO pulleys. I knew something was wrong. I went back for 34" . . . They work nicely.
note: When getting those PTO belts, get a matched set. Napa has a heavy duty v-belt that's green. I think their designed for garden tractors.:fing32:
 

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The Magnificent
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Hold up a second Rick. The very early ones were 3/8" belts. I have a hand written note in one of my manuals about a particular year being the first with 1/2" belts.

Which year do you have here? Maybe remeasure those pulleys again and see if the 1/2" fits the groove properly.
 

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I have a spare PTO with those narrower 3/8" belts. Those pulleys are more noticeably smaller. Your not going to put 1/2" belts on those pulleys without them sitting way tall in the grooves .
The 3 different manuals I have say the PTO belt is 1/2 x33". That size is wrong. 1/2 x 34" would be the correct size.

Maybe the 3/8" belts were 33" for the 3/8 pulleys. Then when they changed them to 1/2" they didn't interpret the manual correctly.
 

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The Magnificent
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I'm curious about that as well Z. My son's Unico definitely has the 1/2" pulleys, and from what I can tell the 15 HP was only produced in 1972.

Could there have been a recall?
 

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My MTD990 is a 1974 and it takes the 3/8" Belts. When you change them spend the extra money and get a good set.
Do you know the length of those 3/8" belts that's on your tractor? I would recommend that to anybody who changes those PTO belts.
 

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There are two different PTO systems; the earliest used the 3/8" belts and "stretched" the belt outwards to engage; the idler pulley will be grooved for the belt. The later design pulls the belt inward with the idler pulley riding on the outside of the belts.

The earlier design is useless if you want to use a tiller; it'll eat the belts in a jiffy. DAMHIKT.
 

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Discussion Starter · #11 ·
Much Thanks to all!
A 3/8" wide UNUSED belt sits well below the outside dia. of the pulley, about 3/16" on a side. Close to bottoming out, probably would with just a few working hours on it.
An UNUSED 1/2" wide belt is barely proud of the OD. Maybe 1/32".

The old 34" long WORN belts apparently started life as 1/2" wide and were still working, engauging and disengauging as the should have. These old worn belts sat just below the pulley dia. Looked like that was how they were supposed to be,... and leading me to believe that this particular 990 takes 1/2" wide belts and they should be 34".
Haven't got the new 34" belts yet cause I had to go to the *&%# dentist
I am very grateful for everyone here helping me hash this problem out. Thank You, Rick
 
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