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Do you like the Magnum series engines by Kohler?

  • Yes, Their OK

    Votes: 3 30.0%
  • Yes, one of the best engines availible for the period.

    Votes: 5 50.0%
  • Yes, my wife gave birth to one!

    Votes: 1 10.0%
  • No, they are junk.

    Votes: 1 10.0%
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Discussion Starter · #1 ·
Hello, I just bought a 1987 Ariens GT20 with a Kohler Magnum 20hp engine... I've looked around quite a bit on this forum but can't seem to find if this m20s passes the test of the die-hard GT fans... I'm hoping that it's a great motor and last a long time. I change the oil every 25 hours and the filter every 50 just like recommended. It's been well cared for by it's original owner and has almost 8000 hours on it, although you would never know it to look at it. Is this motor popular or is it one of those, "Oh no it's an m20, to bad."...

Peace, Dwaino
 

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The Kohler Magnum Twin is tough as nails. I have never seen one with a "ventilated block" or even one that was locked up. This is largely due to a cast iron block and full pressure lubrication. The only weakness that I know of is that you need to "keep feeding them carburators" as the shop foreman where I work says. I have a M18 and several of my friends have M18's and they just seem to go forever. JMO but I think you will be very happy. However, at 8000 hours, it has probably been overhauled at least once. Even the best commercial application air cooled small engine is rated as a 5000 hour expected engine life before a major overhaul is required. A Liquid Cooled, however, like a Kawasaki FD or a Kohler Aegis, is rated as a 10,000 hour engine.
 

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Discussion Starter · #4 ·
Well, it was well cared for. If you look at all of the periodic maintenance in the service manual, it has checks and specs for when and why to replace, inspection and reconditioning, it's very extensive. If a mechanic in a shop committed to his fleet of equipment did things by the book then this motor has been apart several times. It runs great and doesn't smoke or use oil. I kept forgetting to check the hour meter until after I bought it and got it home. To look at it one might it has a couple of thousand hours at most. I was quite shocked to see 7887.50 hours on it. Maybe it's been short-blocked a time or 2... What is the average time to expect from a large twin small engine?
 

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Discussion Starter · #5 ·
Hope you're right Onan18... I'm very happy with it. Hope it stays that way. I have good instinct with things like this and I feel this is a good one. Like I say it runs great. Very strong and responsive. The governor is right on the money as it keeps the same rpm as the load changes. I did have to take the carb apart and clean out the bowl after about three hours. It would spit and sputter when it warmed up. But once the carb was cleaned, it has run as smooth as could be ever since. I've put about 12 hours on it.
 

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On average as I said before if properly cared for around 5000 run hours before a major overhaul is Required. A compression and a leakdown test will give you a good indication of when the last overhaul was performed. Typically, when an engine is shortblocked there is a tag on it that reads something to the effect of "NOTE: This engine has been short blocked. Please refer to short block part number XXX XXXXXXX XX when ordering any related parts." I am not too terribly familar with the Magnum but I do know that an Onan has enough meat in the block that they can be bored 0.040" with no ill effects. So even if you have to bore 0.010" on each overhaul, which is not always the case with a cast iron engine; sometimes a good hone and new rings is all that is required, you can still get four overhauls out of a block. So it is possible for the service life of a block, if properly maintained, to be 25,000+ run hours. So CHANGE YOUR OIL!!!!!!!!!!! I am kinda picky, I change my filter at every oil change. Good Luck.
 

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The Kohler Magnum Twin is tough as nails. I have never seen one with a "ventilated block" or even one that was locked up. This is largely due to a cast iron block and full pressure lubrication. The only weakness that I know of is that you need to "keep feeding them carburators" as the shop foreman where I work says. I have a M18 and several of my friends have M18's and they just seem to go forever. JMO but I think you will be very happy. However, at 8000 hours, it has probably been overhauled at least once. Even the best commercial application air cooled small engine is rated as a 5000 hour expected engine life before a major overhaul is required. A Liquid Cooled, however, like a Kawasaki FD or a Kohler Aegis, is rated as a 10,000 hour engine.
What? I've seen plenty of ventilated block in the Kohler Magnum line. Models M18S and M20S. Neither of those are cast iron blocks. They are Al blocks with cast iron jugs. It is the KT series engines that were cast iron blocks. And 2500 hour with proper care is more likely to be the case between overhauls. The 8000 hours is likely from a key being left on and the clock running.
 

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Discussion Starter · #8 ·
The key left on has crossed my mind. That may account for some. Let say the key is on and the rig is not running. It might last two day before the battery goes flat. So there is 50 hours. 20 times is a 1000 hours. Would someone who cared for something so meticulously be so careless as to leave the key of so many times? Maybe the caregiver wasn't the operator...So if I pull one of the heads and measure the cylinder diameter and it's .020 over. then I could assume that it's been overhauled at least twice right? Also I'll check the manufactures tag and see if it's the original engine...

Hey, thanks for all the input everyone. It's a big help...
 

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Discussion Starter · #9 · (Edited)
Oh yeah, what is a "ventilated block" by the way? I change the oil...
OIL IS CHEAPER THAN IRON! I was taught as a boy...
 

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No offense Fla. Don, but my M18S has rust on the cooling fins of the block. Aluminum does not rust. A Magnum does, however, have aluminum heads. Go to kohlerengines.com and it says "Born of heavy-duty cast iron, KOHLER Magnum engines provide years of durable, reliable performance." Dwaino, a ventilated block is an engine that has thrown a connecting rod clean through the block, leaving a nice "vent," better known as a hole.
 

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Discussion Starter · #11 ·
Well, I checked my engine numbers and it appears that the Kohler magnum serial number starts with a 19 meaning 1989... My Ariens GT serial number is 001763 making it a 1987... I have a feeling it was more than likely a warranty replacement...
 

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That is no big deal, as a matter of fact it can be seen as a good thing. A factory replacement engine is a wonderful thing because most of the time a replacement engine is overbuilt because it is meant to accommodate several applications. So they usually have beefier internals than more base engines so if put into commercial duty they will last longer. At least that has been my experience.

Joe
 

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No offense Fla. Don, but my M18S has rust on the cooling fins of the block. Aluminum does not rust. A Magnum does, however, have aluminum heads. Go to kohlerengines.com and it says "Born of heavy-duty cast iron, KOHLER Magnum engines provide years of durable, reliable performance." Dwaino, a ventilated block is an engine that has thrown a connecting rod clean through the block, leaving a nice "vent," better known as a hole.
Yes they were born of cast iron but that changed. But back in the days of the K, not M series. A Magnum Twin engine has an Aluminium Crankcase, Cast Iron cylinder jug, and Al heads. You will find the nuts that hold the cylinder jug to the crankcase on the lower flange of the jug ( barrel per Kohler ). Go to page 99 of http://oldgravelys.net/pdf/Kohler_M18_M20_Serv_Man.pdf to see how they come off of the crankcase. 6 studs in the Al crankcase hold the jugs to the crankcase. Here is what you have on the starter motor side ( #2 cylinder) of the crankcase after you remove the jug.
 

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The key left on has crossed my mind. That may account for some. Let say the key is on and the rig is not running. It might last two day before the battery goes flat. So there is 50 hours. 20 times is a 1000 hours. Would someone who cared for something so meticulously be so careless as to leave the key of so many times? Maybe the caregiver wasn't the operator...So if I pull one of the heads and measure the cylinder diameter and it's .020 over. then I could assume that it's been overhauled at least twice right? Also I'll check the manufactures tag and see if it's the original engine...

Hey, thanks for all the input everyone. It's a big help...
It can be even .030" over and only have been overhauled once. Depending on wear in the cylinder bores, it could take that much to clean up scratches or taper.
 

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If you don't mind me posting it, here's the data on your tractor.

9/09/2010 Ariens Dealer Product History Inquiry 9:51:00 PM


MODEL NUMBER: 931034 SERIAL NUMBER: 001763

DESCRIPTION: T-M20S KE HYD GT

Dealer #: Owner:
Dealer Name: Address:
Ship Date: 3/17/1989 City: WESTBROOK
H D Store: State: ME
Dealer Sales Representative: Zip:
Principal Use: Country: USA
Sold Date: 4/24/1989 Phone:

So that says it is a 1989 unit and still has the original cowls. We have short blocked, long blocked, and just replaced the jugs on engines so until you find a date stamp on the crankcase, you can't assume it ever was replaced.


If you want to pm me just the last name of the person you bought it from, I can tell you if they were the original owner.
 

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Thanks, Fla. Don, that is very cool. So when you said jugs you were referring to the whole thing, I thought you meant they had aluminum castings with cast iron sleeves like a Command. Learn something new every day. So a Magnum twin has cylinder jugs like an old Volkswagen or a motorcycle, cool. I for some reason had always thought that they split in the center like an airplane engine. Thanks for passing on the knowledge.
 

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Thanks, Fla. Don, that is very cool. So when you said jugs you were referring to the whole thing, I thought you meant they had aluminum castings with cast iron sleeves like a Command. Learn something new every day. So a Magnum twin has cylinder jugs like an old Volkswagen or a motorcycle, cool. I for some reason had always thought that they split in the center like an airplane engine. Thanks for passing on the knowledge.
Kohler made them easy to fix, unless you threw a rod. Which is what three of the ones sitting here had done before I got them. Very common as the governors were a weak link. They'd over rev. Then a ventilated crankcase. The crankcase does split in two so that you can use ball bearings for the crankshaft. Gravely Ls and Cs also use a cast iron jug in a Tee configuration.
 

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Discussion Starter · #18 ·
If you don't mind me posting it, here's the data on your tractor.

9/09/2010 Ariens Dealer Product History Inquiry 9:51:00 PM


MODEL NUMBER: 931034 SERIAL NUMBER: 001763

DESCRIPTION: T-M20S KE HYD GT

Dealer #: Owner:
Dealer Name: Address:
Ship Date: 3/17/1989 City: WESTBROOK
H D Store: State: ME
Dealer Sales Representative: Zip:
Principal Use: Country: USA
Sold Date: 4/24/1989 Phone:

So that says it is a 1989 unit and still has the original cowls. We have short blocked, long blocked, and just replaced the jugs on engines so until you find a date stamp on the crankcase, you can't assume it ever was replaced.


If you want to pm me just the last name of the person you bought it from, I can tell you if they were the original owner.
The person I bought it from was the third owner. He owned it for 10 to 12 years. The person he got it from hadn't owned it very long. I thought it was an 1987 because it has a date of May 14th 1987 stamped on the underside of the hood. Maybe the hood was replace with a used one. Also, I know that the unit was serviced by Don's Power Equipment in Portland/Westbrook and was more than likely purchased there as well as they had the Ariens dealership rights for that area for many years. They are now out of business. Like I said before, I believe it was owned by some sort of land association and may have had something to do with a boys camp, home or maybe even the Maine Youth Center (now closed) in So. Portland Maine. At some point I will be in contact with the guy I got it from and will have many questions for him... Can you find the name of the original owner? How did you get that info? I called Don's thinking they would have info on it but they folded about 4 years ago. I use to service Don's with uniforms back in the mid 90's...
 

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Discussion Starter · #19 ·
That is no big deal, as a matter of fact it can be seen as a good thing. A factory replacement engine is a wonderful thing because most of the time a replacement engine is overbuilt because it is meant to accommodate several applications. So they usually have beefier internals than more base engines so if put into commercial duty they will last longer. At least that has been my experience.

Joe
I have heard of this concept. I once bought a hard drive for a slave backup on my computer. It was a Western Digital I believe and I paid around $60 for it new. It failed in the first month so I warrantied it. In searching to find out if this series of hard drives where junk I found a lot of people saying the warranty replacements where highly sought after and worth 4 times what I originally paid. I looked on ebay and found the one I had for about the same money I paid. I also found the one everyone was raving about for 2 to 3 hundred dollars. When I got my replacement, sure enough it was one of those highly sought after ones. I guess the fail rate isn't even on the chart... I put it in my computer and it's never had a single problem.

I would add though, the GT20 is already a commercial product. It seems these things weren't intended for the average homeowner or the neighborhood lawn mower boy (me as a kid)... These things where made to devour the chores associated with huge tracts of land. Kohler may have still used sandbag motors on warranty replacements to insure the customer didn't render Kohler as junk with a second motor failure... But as far as the Ariens GT20 goes, how could it have been made any tougher... I could monster stomp all of my friends riders in a leisure afternoon and wake up and stomp their snowblowers for breakfast...
 

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The person I bought it from was the third owner. He owned it for 10 to 12 years. The person he got it from hadn't owned it very long. I thought it was an 1987 because it has a date of May 14th 1987 stamped on the underside of the hood. Maybe the hood was replace with a used one. Also, I know that the unit was serviced by Don's Power Equipment in Portland/Westbrook and was more than likely purchased there as well as they had the Ariens dealership rights for that area for many years. They are now out of business. Like I said before, I believe it was owned by some sort of land association and may have had something to do with a boys camp, home or maybe even the Maine Youth Center (now closed) in So. Portland Maine. At some point I will be in contact with the guy I got it from and will have many questions for him... Can you find the name of the original owner? How did you get that info? I called Don's thinking they would have info on it but they folded about 4 years ago. I use to service Don's with uniforms back in the mid 90's...
I have dealership access to Gravely's/Ariens' website. One thing I'm restricted on is the original owner's names. I can see it and their addresses/phone numbers but not allowed to give them out. If asked, I can say if they are/were the original owners.
 
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