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I have a 42” JD Snow thrower, Ser # M03250X120429. Based on the plate, I think the model number is 42 Snowthro-200. My yard tractor is a JD 345. I purchased this snow thrower new when I bought the tractor, about 20-25 years ago. This thrower uses 1 belt only, not two. The auger is run with a chain before JD modified this model to use two belts.

When I got the thrower, the belt on the unit was a HB heavy-duty belt. I would like to replace it, but I am having trouble finding the correct HB belt size. Based on searching, I am not the only one who has had this trouble. Our dealer wants to sell me a M72112 belt which will fit but is a HA belt, not what I am looking for. M72112 is same belt number I keep finding when I search for a replacement belt.

I did try a heavy-duty belt from our local dealer, but it was way too long. She then told me the HB belt was discontinued. I spoke to a JD online supplier who said the replacement belt I need is a M131766. I do not believe this is correct because that is also a HA belt and longer then the M72112 belt. Does anyone know what it the correct belt number I need?

I did find this link that maybe helpful, but I am not sure how to measure for a HB belt. The M72112 is about 116" long, inside measurement. Would that be too short for a HB belt? Any help would be appreciated.

https://www.greenpartstore.com/assets/images/guides/2014/BeltGuide.pdf
 

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My chain drive 42" M0321X151918 uses a 116" belt. I've had much better luck with an aftermarket Kevlar belt, PIK-A114K.
I don't know what you mean by HA and HB.
 

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V-belts look pretty simple. a v-shaped piece of rubber XXX.XX" long...and that's where the simple stops! I can't solve the OP's question, but I'm certain I can add more confusion!

svobronco, Since you question is the easiest, I'll answer that...easily! HA & HB are cross sections of a belt. An HA belt is 1/2" wide at the top and 11/32" high from top to bottom. An HB belt is 21/32" wide by 7/16" high. Since this is a "wider" belt it will ride higher in the groove on the pulleys.

Getting back to OP's question, he states his belt is 116" inside dimension. However, belts are spec'd by "effective length" or the length of the belt at the pitch diameter, pitch diameter being a point on the midpoint of the belt where it makes contact with the pulley. The M72112 is an HA belt and has an effective length of 116.14" per OP's attached chart.

Another consideration is the angle of the belt! JD uses approx. a 32º included angle on their pulleys and belts and most off the shelf belts are 40º. Since the belts are a similar cross section, an off the shelf belt, when first installed, will only drive by the very top of the belt. This quickly wears and the belt goes deeper into the groove until 100% contact is made along the sides of the belt or the belt bottoms out on the pulley. This is why JD belts last longer, they fit correctly!

Going back into the chart the OP posted, the M72112 HA belt is 116.14", and an HB belt, M122821 is 116.02. Since the HB is wider, it will ride higher in the pulley groove and may be too short, don't know for certain. There may (??) be enough adjust in the belt tensioning to compensate the technically shorter & wider belt, but don't know. If it was me, I'd try it! Bob
 
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