hmsk80 vs. hmsk100 - Snowblower Forum : Snow Blower Forums
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post #1 of 33 Old 02-24-2015, 06:34 PM Thread Starter
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hmsk80 vs. hmsk100

I blew the engine in my mtd 10/24 snow blower last year. it originally had a hmsk100 but all I could find at the time was a hmsk80 to replace it with. the hmsk80 I bought blows away the hmsk100 that was originally on the blower but I also turned the governor on it up to 3600rpm. im assuming the hmsk100 was down on power since it had the original oil from 2003(blower was given to me) and seized. im wondering if it would be worth it to find another hmsk100. is there a noticeable difference in power? ive already installed an impeller kit and have a 1/2" larger engine pulley to spin the auger impeller faster on the way. the hmsk100 makes an additional 3ft/lbs of torque and is 40cc's bigger. opinions? I really want to throw some snow since my driveway is 5-6 cars wide and I can only throw in one direction. thanks in advance.
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post #2 of 33 Old 02-24-2015, 06:40 PM
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24" blowers normally have engines between 5 and 8 HP. Distance is a factor of tight impeller tollerances (impeller kit), impeller rpm (oversized pulley) and clean slick chutes (sand, paint and wax).

The larger impeller pulley might benefit from a larger engine if you have a lot of heavy snow and the engine is bogging down. If your engine doesn't bog down then more power will do absolutely nothing for you.

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post #3 of 33 Old 02-24-2015, 08:55 PM
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I understand the nice feeling of having a little power to spare as I like that too, but that 8 should do just fine if the impeller bearing is good, and the impeller kit is installed to sweep clean with minimum drag. It should keep you happy.

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post #4 of 33 Old 02-25-2015, 06:50 AM
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Quote:
Originally Posted by cadmobile500 View Post
I blew the engine in my mtd 10/24 snow blower last year. it originally had a hmsk100 but all I could find at the time was a hmsk80 to replace it with. the hmsk80 I bought blows away the hmsk100 that was originally on the blower but I also turned the governor on it up to 3600rpm. im assuming the hmsk100 was down on power since it had the original oil from 2003(blower was given to me) and seized. im wondering if it would be worth it to find another hmsk100. is there a noticeable difference in power? ive already installed an impeller kit and have a 1/2" larger engine pulley to spin the auger impeller faster on the way. the hmsk100 makes an additional 3ft/lbs of torque and is 40cc's bigger. opinions? I really want to throw some snow since my driveway is 5-6 cars wide and I can only throw in one direction. thanks in advance.
this past week I did some of those exact tests, the AMF 8HP Tec. vs. the AMF/Craftsman 10HP Tec.

the 10HP engine cut through the frozen 14" snow better than the 8HP, and when it hit the deep frozen stuff, the 10HP was not pulled down in rpm a much

the 8HP was close but the 10HP was noticeably more powerful.

you discovered a well kept little secret amongst snowblowers and small engines- reset the governor WOT speed higher and you get more performance from the machine. the factory governor settings are always on the conservative side. the engines are capable of more rpm and power within sane limits. they keep the rpm down to extend engine life and limit warranty work issues.




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post #5 of 33 Old 02-25-2015, 11:20 AM
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you discovered a well kept little secret amongst snowblowers and small engines- reset the governor WOT speed higher and you get more performance from the machine. the factory governor settings are always on the conservative side. the engines are capable of more rpm and power within sane limits. they keep the rpm down to extend engine life and limit warranty work issues.
The other thing is the governors are controlled by springs. As the springs get older they get stretched out and loose tension which slows the engines down even more.

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post #6 of 33 Old 02-25-2015, 03:34 PM Thread Starter
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thanks for everyone's input. the pulley came today. I will hopefully put it on tomorrow. hopefully well get some fresh snow soon. everything here is dry and crunchy.
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post #7 of 33 Old 02-25-2015, 04:55 PM
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You can't tell the difference between an 8hp and 10hp Tecumseh. I've swapped one for the other before on the same machine, you can't tell the difference, and to be totally honest with you I'm not sure there is one, I'll have to check some part numbers.
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post #8 of 33 Old 02-25-2015, 05:21 PM Thread Starter
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they are not physically identical.
the hmsk80 has a 3.125" bore and the hmsk100 has a 3.531" bore. other than that they are identical. same cam, crank and carb.
this is why the hmsk100 makes an additional and 3ft/lbs of torque and does it 500rpm lower than the hmsk80. its limited by the cam...
were talking 20% more hp and torque.
my question is, can you tell the difference? is it worth it?
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post #9 of 33 Old 02-25-2015, 07:17 PM
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I went from a 24" Ariens with an HMSK80 (8hp L-head) to a 24" Ariens with an OHSK100, I think it is (10hp OHV).

Both are 318cc, both are 3.125" bore.

I think the 10hp one had a bit more power when I tried to do a head-to-head comparison last year, but it certainly wasn't an overwhelming difference. It wasn't an ideal comparison, deeper snow would have helped load them up more.

As Shryp said, until you have enough of a load that one engine is at full-throttle, and is still slowing down, you won't see any difference.

I sold the 8hp, so can't do any more comparisons. But reading some things about governor linkages got me wondering. The next time I take the carb-box cover off on the 10hp, I'm going to make sure the governor linkages are connected correctly. I might even try to double-check that the governor arm is adjusted properly on the shaft (when I bought this machine, something on the carb was connected wrong, so it's been messed with a bit).

One challenge I've had with being certain that I'm out-of-power, vs a potential governor issue, is not having any feedback on the engine's throttle position. If the governor was not working right, your RPM may drop under a load, but the engine's not actually at full-throttle.

I've wondered about trying to connect a string to the throttle plate, for testing purposes. When under a heavy load, and the RPM has sagged, give the string a little tug. If nothing happens, you're out of power. If the engine sounds different, then your governor didn't have the throttle open fully.

Part of what got me thinking about this was clearing 8-10" of light snow recently. I wasn't even taking a full 24", but I still heard the engine slow a bit. It got me wondering if that's merely acceptable "sag" in the governor, or if I'm already power-limited. It didn't sound like when going into a big snowbank, so I'm thinking it was related to the governor.

Presumably no mechanical governor is perfect at holding speed exactly as the load varies. My Generac generator manual tells you to set the governor so you get 62-63 Hz with no load. As you add a load, the RPM drops closer to 60 Hz (3600 RPM).

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post #10 of 33 Old 02-26-2015, 06:39 AM
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Quote:
Originally Posted by Shryp View Post
The other thing is the governors are controlled by springs. As the springs get older they get stretched out and loose tension which slows the engines down even more.
bingo give that man a cigar...standard procedure here on these very old machines is, cut one coil off the governor spring, and re-attach it to increase tension. or, move it to a hole that is farther away, increasing tension. or in very few cases, there is a screw you can adjust to increase governor spring tension. or finally if you can, replace it with a new one that is oem correct for the engine.

the interface with the operator controls is what wears out on these machines. i.e. the control handles, springs, cables. a weak spring makes the engine hunt up/down in rpm.
installing a new control plate with tight throttle stops and new governor spring, made a world of difference on my AMF Dynamark. it went from being a quirky machine, to rock solid powerful machine that holds steady rpm at idle, and wide open throttle.




just say NO to Chinese made ANYTHING !
1967 S-242 Snowbird 4/24
AMF Dynamark Luminaire 5362 8/26 3-stage
Craftsman Drift Breaker 10/32 3-stage
Gilson 55012 8/26 gear drive
Ariens 910010 8/32
Cub Cadet 268 8/26
Yard-Man Snowbird 7040-0 5/22
Ariens 10M-L35 3.5/24
New Holland/Gilson Unitrol 8/26
(2) AMF Polar Bear 7/26 3-stage project/parts machines

Last edited by greatwhitebuffalo; 02-26-2015 at 06:41 AM.
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