# Upgrading Engine on HSXXX models



## Jman444 (Dec 20, 2020)

Hello everyone,
I'm sorry if this has been asked before, I could not find it. I am looking at getting an HSXXX model snowblower. I wanted to know if there was any difference in these machines besides the engine size. I'm considering getting an HS624 or HS724 for example and putting a more powerful engine on it. Is it as simple as dropping it in or do I have to worry about upgrading the friction plate or any other size constraints etc.

Thanks for your help.


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## ST1100A (Feb 7, 2015)

All of those Honda models are hydrostatic driven so you don't have to worry about any friction plates.
You might have to install longer belts on a HS624 and relocate the chute turn handle if you drop in the motor out of a HS1332 because of its larger external size.


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## orangputeh (Nov 24, 2016)

well, an HS624-724 does not have a friction disk drive. It has a hydrostatic tranny which is much better. I have read here that you can put a 8 ( gx240 ) or 9HP ( gx270 ) on this chassis but I think you have to cut off mounting studs and weld on new ones to fit the bolt pattern of the 8-9.

not sure though. I have put 11hp ( gx 340 ) engines on an 8 and 9 HP Honda chassis but all 3 of those engines have the same bolt patterns. 

somebody will come along with a better answer


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## AK_Beag (Dec 23, 2020)

How big you going? I finished upgrading an HS624 to a 7hp 212cc Lifan engine. Pretty much all bolted up, with the only catch being the original Honda engine has a metric output shaft and pulleys. I was able to reuse the metric pulley on the new 3/4" shaft by making a shim from aluminum flashing and using some Loctite 660. Since the outer dimensions of the engine were the same, there was no difference in belt size.


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## ST1100A (Feb 7, 2015)

That could be a big costly mistake using aluminum flashing as a shim. When the soft aluminum metal shim crushes down and the pulley becomes out of round/out of balance, you will be destroying bearings on the transmission, the auger, and the engine itself. 
Soft aluminum shims between hard steel parts don't work well under the pressure they will be subjected to.
You will have to get a custom key-way, rectangular shaped, not square to fit snug or you will ruin it in a hurry.
Your best bet would be to have a pulley custom made/machined to fit semi snug on the crankshaft to transfer power, because if that becomes the ever so slightest out of round and spinning at crankshaft speeds, it will throw everything out of balance and you will be looking at a new snowblower from the cost of damage that is going to happen to it.


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## AK_Beag (Dec 23, 2020)

Yeah, that's not been a problem since I'm using the Loctite 660, it'll fill bond gaps up to 0.5mm and glues it as one solid piece. It's those gaps or play that bash a shim apart. I've been using it for a year with no problems. Without the 660, the mismatched keyway would absolutely fail first, there really is not enough lateral load from the belts to outright crush the shim. That being said OP, if you're looking at going with a bigger engine (that might have a 1-inch shaft), you're going to want new pulleys anyway. 1-inch and 3/4-inch A and B belt pulleys are readily available off the shelf, and nothing needs to be custom machined. You also might want to consider a slightly smaller auger pulley will help put that new power to work.


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## orangputeh (Nov 24, 2016)

AK_Beag said:


> Yeah, that's not been a problem since I'm using the Loctite 660, it'll fill bond gaps up to 0.5mm and glues it as one solid piece. It's those gaps or play that bash a shim apart. I've been using it for a year with no problems. Without the 660, the mismatched keyway would absolutely fail first, there really is not enough lateral load from the belts to outright crush the shim. That being said OP, if you're looking at going with a bigger engine (that might have a 1-inch shaft), you're going to want new pulleys anyway. 1-inch and 3/4-inch A and B belt pulleys are readily available off the shelf, and nothing needs to be custom machined. You also might want to consider a slightly smaller auger pulley will help put that new power to work.


hmm . I get ******* fixes but not on a critical part like this.

@ST1100A knows what he is talking about. 

I charge double in my shop for screwed up ******* fixes and tell people upfront.


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## ST1100A (Feb 7, 2015)

I have seen many of those red neck fixes, and collars crush or loosen causing major problems.
The fix he mentioned might work for a little while but I would not trust it from many things I have seen happen from people that did that.
I would be afraid to Glue the pieces together, although it may help temporarily, but when it comes time to take them apart and they are stuck together, there's a lot of extra work to take them back apart, and then you are risking more damage disassembling them.
He has the right idea of the bigger engine, smaller auger driven pulley to spin the impeller faster for a further throw, as long as the rest of the gearboxes and bearings can take the extra speed. They will be wearing out a little bit faster than at a slower speed.
I would probably leave the pulley size be, because the extra power from the bigger engine wont slow down as much as the smaller motor would so the stock speed should be fine.


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## AK_Beag (Dec 23, 2020)

I'll keep that in mind when I take it to my A&P for it's annual.
I got my machine for free with a half worn auger, so I spent accordingly. Loctite 660 is made to do this and just needs heat to release, it's not like I used JB Weld. OP may be building up something nicer, so a metric shaft GX270 may be on his short list, I don't know.

OP, swap info can be found using google and limiting to this fourm. swap hs624 site:www.snowblowerforum.com - Google Search

The best thread I found in a quick search was Installing a GX340 on HS624


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## tabora (Mar 1, 2017)

AK_Beag said:


> making a shim from aluminum flashing


I'd always use 316 stainless shim stock over aluminum in that application.


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## AK_Beag (Dec 23, 2020)

tabora said:


> I'd always use 316 stainless shim stock over aluminum in that application.


Good to know that's available, I'll add some 0.002 inch to my shopping list to replace the aluminum


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## ST1100A (Feb 7, 2015)

AK_Beag said:


> Good to know that's available, I'll add some 0.002 inch to my shopping list to replace the aluminum


That's what you want to use, plus it has less chance to corrode and stick fast to the other steels of the crank and pulley, and less chance of crushing, it is much stronger and durable.
Every time you engage a pulley, whether it be the auger under a load or the propel drive transmission you put a serious shock load on the pulley that will damage the softer metal.
You will have better results with that than the aluminum.
Thanks to @tabora for that good recommendation.


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## RikP (Jan 19, 2021)

I am doing this upgrade: HS724 -> HS924.
Will I do it again ? Never.
It's almost finish. Here are my conclusions :

Engine bolts size and pattern is not the same for 6 / 7 hp vs 9 / 11 hp.
9 / 11 hp have a bigger camshaft. You will need to find new pulleys.
Bigger engine are higher so, you will need longer belts. It's ok for the drive, but you will need to find non Honda for auger as it will take an SB37 instead of the standard SB35
Remember that the auger driven pulley is lower on a HS724 / HS624 than on on a HS929

You will need to fit a new belt cover because engine pulleys are 1 inch higher on bigger engine.
You may tempted to move the tension arm to the higher holes and to fit a HS928 wire holder. Do not do it. Because the auger is lower on an HS6 / 7 , you will not be able to bolt the auger housing to the bed.

You will need to ajust the upper chute handle bracket position because the lower chute handle is longer for an HS928 +
More to come...


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## IndianaRidgeline (Dec 15, 2020)

I tip my hat to you guys who are true fabricators. I appreciate your talents and wisdom to problem solve thinking through so many variables. You have a gift, which can't be taught. Thank you for sharing to us amateurs who are learning.


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