# Honda HS724 Shear Bolt



## Sportage71 (Feb 8, 2021)

My HS724, tread style, purchased in 2004....in great condition.
This year the bolt lock 90102-732-010 goes thru the impeller shaft/drive shaft has sheared off 3x
The shear bolts on the auger etc are all good but this bolt is shearing frequently, never has before.
Why is this happening? It is so difficult to replace as well because have to knock it out, as it shears & the pin of the bolt is left in the shaft.;hard to get at behind the augers.
Comments, help????


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## tabora (Mar 1, 2017)

I assume they are OEM Honda black oxide with the step head, correct? Non OEM step bolts or bolts without the step shear pretty easily when a chunk of ice gets back there. The OEM ones are 10.9 hardness, and you should use the flange lock nuts with them. Reminds me, I've got some I need to sell off soon...

If the impeller bearing is going, that can also lead to that bolt shearing.








Avoid these and other non-OEM bolts:


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## Sportage71 (Feb 8, 2021)

tabora said:


> I assume they are OEM Honda black oxide with the step head, correct? Non OEM step bolts or bolts without the step shear pretty easily when a chunk of ice gets back there. The OEM ones are 10.9 hardness. I've got some I need to sell off soon...
> 
> If the impeller bearing is going, that can also lead to that bolt shearing.


Hi tabora. Yes, the step head bolts 6mm with lock nut. I do use those purchased from Honda dealership but they are shearing constantly. & not easy to put back in.
However, have put them in several times now. Why are they shearing so much? Always shear off the step head & threaded bolt section leaving pin in the shaft! Wish I knew why they are shearing???? These QEM Honda bolts defective? Soft?


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## orangputeh (Nov 24, 2016)

Sportage71 said:


> Hi tabora. Yes, the step head bolts 6mm with lock nut. I do use those purchased from Honda dealership but they are shearing constantly. & not easy to put back in.
> However, have put them in several times now. Why are they shearing so much? Always shear off the step head & threaded bolt section leaving pin in the shaft! Wish I knew why they are shearing???? These QEM Honda bolts defective? Soft?


@tabora suggested a possible reason. impeller bearing. any excess play on impeller? long shot reason would be the holes that the shear goes into are elongated so the bolt bang around a bunch and breaks. 

if there is too much impeller play , the bucket has to be removed to replace impeller bearing. I would also replace belts if needed. also remove auger assembly/ impeller and eyeball the holes on impeller. if egg shaped , weld up bad area and drill a round hole. back. 

bad batch? possible. doubt it if OEM.


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## Arcticnorth (Nov 27, 2020)

Sportage71 said:


> Wish I knew why they are shearing????


Like tabora said, it could be the impeller bearing. Not unlikely on a 16 year old. You need to split the machine (remove the auger housing) to change it. I did that on mine, it's fairly straightforward. And while you have it split, change the auger belt as well.


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## Toro-8-2-4 (Dec 28, 2013)

tabora said:


> The OEM ones are 10.9 hardness, and you should use the flange lock nuts with them.
> 
> If the impeller bearing is going, that can also lead to that bolt shearing.
> 
> ...


 Class 10.9 shear bolts? Those are strong. Seems odd, but Honda like to pave their own way. 
Also odd is MTD is into the Honda replacement parts business.


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## Sportage71 (Feb 8, 2021)

What do you mean by impeller play? How can I see how to split the M/C, how long?


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## Sportage71 (Feb 8, 2021)

Toro-8-2-4 said:


> Class 10.9 shear bolts? Those are strong. Seems odd, but Honda like to pave their own way.
> Also odd is MTD is into the Honda replacement parts business.


agreed Toro


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## tabora (Mar 1, 2017)

Toro-8-2-4 said:


> Seems odd


Not odd at all... Harder bolt = cleaner shear. They're only 6mm. Here's the info Honda provided about the current HSS shear bolts:

The impeller shear bolts are all the same on all HSS-series 2-stage machines.​​• There is not a published spec for the torque required to break a shear bolt.​• The shear bolts are specially designed 6x18mm carriage bolt with a metric class 10.9 strength rating. This strength rating is 940 MPa min yield strength (136,000 psi) and 1040 Mpa min tensile strength (151,000 psi).​• Honda does recommend you use only Honda shear bolts; there is a risk a non-Honda shear bolt may not 'shear' when it is supposed to.​ 

90119-V45-A00BOLT, SPECIAL (6X18) - Auger Shear
 

90121-V45-A00BOLT, CARRIAGE (6X18) - Impeller Shear


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## Toro-8-2-4 (Dec 28, 2013)

Interesting.. Even the auger sheer bolts are class 10.9! I still say it is odd relative to the most common non Honda machines we see here in the US. I do not doubt they did their home work.


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## ST1100A (Feb 7, 2015)

The '10.9' is a Metric rating, NOT an S.A.E. rating.
It is also a 'Hardness rating, not a tension strength rating, big difference there.
There is a difference between Metric and S.A.E. ratings. '10.9' is not a S.A.E 'Grade 10' like a 'Grade 8' bolt or shear pin that MTD/Cub Cadet uses that causes broken worm gear shafts.
They are probably closer to an S.A.E. grade 3-5 on the bolt tension but are more 'Brittle' so they snap easier. If they were a S.A.E. grade 10, they would be braking shafts like crazy among other parts like the auger tubes and breaking gearbox gears like crazy.


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## Freezn (Mar 1, 2014)

Make sure you're torqueing the impeller sheer pins and auger sheer pins to spec. They should be snug plus 1/4 turn. Can't remember the exact torque spec off the top of my head, but pretty sure it's somewhere around 11 - 13 ft/lbs. ???


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## Toro-8-2-4 (Dec 28, 2013)

This has somewhat intriqued me and did some reading up on it. At first it seemed counter intuitive to me and I think for many. It now makes more sense that a stronger and harder pin makes for a better shear pin. Shear pin testing has shown Softer or more ductile steels have a wider range of where they break. Because they tend to yield more before braking they can often work harden. If they work harden, they break with a higher force value than expected. With a harder or more brittle material the failure points fall in to a tighter range and is more predictable. The Honda pin that is a class 10.9 material and has a 6mm diameter makes more sense. At least from a reliability point of view. The step in the pin also helps it break easier riight at the transition of the step. The step creates a stress riser. The only reason I can think of that the aftermarket pins do not work reliably is that they use what ever 10.9 material they can get. The ISO class 10.9 spec is a minimum tenisle strenght of 1040 MPa and a hardness range of 32 to 39 Rockewell C. My guess is that Honda uses a tighter specs on their pins. But I am speculating. Interesting engineering problem. I'm sure Honda did there homework.


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## drmerdp (Feb 9, 2014)

Heres another consideration. Soft bolts will bend and flex getting extremely stuck in the shaft. A higher hardness on a smaller diameter bolt with shear much cleaner while still protecting the components down the line. And itll be less challenging to remove the shank from the shaft.


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