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00Formula

Re-powering a Simplicity Sunstar

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00Formula

I'm looking for a Simplicity Sunstar but there aren't many in the south, most are in the OH,PA,MI area. I'd like to find a Sunstar with a Kohler Command and the locking diff, but that seems pretty rare. Most with the locking diff have the Magnum engine. That being the case it seems like finding a Sunstar with a blown Onan or Magnum engine and swapping in a newer Kohler might be the best option. Looking around the highest hp Kohler replacement engine advertised for a Sunstar is the 23hp Kohler. Looking at the dimensions of the crank though a 25hp or maybe even the 27hp are possible swaps. I'd really like to throw in the 27hp if it would fit as it could then support a PTO chipper. Has anyone swapped in a 27hp Kohler like this?

https://www.jackssmallengines.com/small_engine_model.cfm?product_id_number=1154&type=Horizontal

The dimensions look identical to the 23hp.

http://www.northerntool.com/shop/tools/product_200310303_200310303

I know the stock air filter would probably be an issue, but I could probably modify it to fit under the hood.

Edit: It looks like the 30hp CH750 is technically the largest and highest hp replacement Kohler engine with the same dimensions as a stock engine.

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RayS

I don`t think they ever used an Onan in a Sunstar. I could look in my engine manual that goes back to the 70`s, but I doubt it. A 20hp Command would run your PTO chipper fine as well. A 25hp or 27hp more than likely will fit without issues. There is a member here that has a 27hp in a 7100 series which is smaller than the Sunstar.

Welcome to the club!

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huffy
quote:Originally posted by 00Formula

Looking around the highest hp Kohler advertised for a Sunstar is the 23hp Kohler.


id="quote">
id="quote">I wasn't aware that they ever made the SS with a 23hp. I thought 20 was the highest.I think BLT's got a 20hp Command listed in the Classifieds.

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maxtorman1234

The largest stock engine was the 20HP Kohler Command or Magnum. The 18HP Command right through to the 27HP have the same exterior dimensions. I (and other members here) have had a 25HP in one before without issue. If the crank size is the same, it's just a matter of wiring. And you could always swap out the industrial air cleaner for the regular factory one. I have 2 1920 Agco's with the Command engines. I have upgraded one to a CH23. Both run great and are plenty of power for even the 60" mower deck.

From what I've found, up to 1992 had Kohler Magnum engines, I have a 1993 and I believe that is when they switched to the Command. It has the differential lock, and has the same tires and knobs as the old Deutz Ultima/Sunstar. The 1996 & 1997 Agco for sure do not have the diff lock. I have a 1996 and installed a diff lock transmission from another 1920. They have the new tires and knobs as well. I Have never seen one with the Briggs engine, but apparently they are out there.

I also have an 87 Deutz Ultima with the Magnum 20 engine. I would not part with that machine, the Magnum is much nicer for working with the blade or hauling logs ect. They are bulletproof as well if maintained, but the Command is generally smoother and quieter.

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00Formula
quote:Originally posted by maxtorman1234

I also have an 87 Deutz Ultima with the Magnum 20 engine. I would not part with that machine, the Magnum is much nicer for working with the blade or hauling logs ect. They are bulletproof as well if maintained, but the Command is generally smoother and quieter.


id="quote">
id="quote">Looking at the engine dimensions the 20hp Magnum was a big engine, 47ci or 770cc, so it could very well have more torque and area under the curve. A quick search didn't turn up the rated torque of a 20hp Magnum, but I would bet it's ~42-44 ft/lbs given the Magnum 18hp was a 42ci engine and rated at 39 ft/lbs. The 20hp Kohler is only a 38ci, or 624cc engine, so it probably has less torque. For reference the largest current Kohler Command of the same exterior size as the stock 18/20hp is 45ci or 747cc, and rated at 30hp and 44ft/lbs. My concern with a Magnum powered Sunstar is that the engine is obsolete, and the tractor attached to it will be older. If it already has a Command, a replacement engine can be swapped in pretty easily.

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CarlH

The Kohler Command twins from 18 HP through 27 HP all have the same external block dimensions and share the stroke length. 18 - 22 had a common bore and 25 - 27 had a different common bore. HP rating depended on cam and carburetor (and maybe ignition timing?). (I haven't looked at the 30 HP Commands.) The only thing to look for is the correct crankshaft PTO end length and diameter. The Command used in the Sunstar had 1 1/8" diameter and 2.87" length PTO end.

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acfarmer

I have Sunstars with the Command and Magnum engines and much perfer the Magnum engines as they are less tempermental and have more power at low RPM than the Commands do.

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Brettw

Unless there isn't enough HP in the Magnum series, I see no reason to necessarily avoid them. Either way, whatever you swap with, I would make sure of shaft size and length, and keep in mind clutch and PTO issues. That may be your biggest issue, along with driveshaft length.

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huffy

My SS has the 20 hp Magnum. It's got plenty of power. I understand the OP's concern about the Magnum having been discontinued. But, from what I've seen parts are readily available.

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maxtorman1234
quote:Originally posted by 00Formula

Looking at the engine dimensions the 20hp Magnum was a big engine, 47ci or 770cc, so it could very well have more torque and area under the curve. A quick search didn't turn up the rated torque of a 20hp Magnum, but I would bet it's ~42-44 ft/lbs given the Magnum 18hp was a 42ci engine and rated at 39 ft/lbs. The 20hp Kohler is only a 38ci, or 624cc engine, so it probably has less torque. For reference the largest current Kohler Command of the same exterior size as the stock 18/20hp is 45ci or 747cc, and rated at 30hp and 44ft/lbs. My concern with a Magnum powered Sunstar is that the engine is obsolete, and the tractor attached to it will be older. If it already has a Command, a replacement engine can be swapped in pretty easily.


id="quote">
id="quote">I think you may have been looking at the Newton meters side of the torque spec chart though, as the M20 has approx. 34ftlbs of torque, and the M18 only 29. I asked kohler for the specs, and they gave me them. (Unlike Briggs, who refuses to tell you the torque. I have found some charts for the vanguard engines, and they are typically a couple ftlbs lower). The Command 20 has approx. 32ftlbs and the 18 about 31ftlbs according to the kohler site. Having run all of these engines, the M18 feels a little low on power and torque, but the Command 20 handles a 60" deck quite well. The Magnum definitely does have more torque at lower rpm's where as the Command pretty much likes to be run wide open. Running the Mangum lower but still having the governor work seems to provide plenty of power for using the dozer blade ect and save fuel over the command. Either engine handles cutting grass and blowing snow without problem, I only run short of power when hauling logs out of the bush, or dead trees into the bush as the hills rob power quick. I run ag tires and 80lbs on each wheel. If you can get a good price on a Command, I would go that route, as they seem bulletproof as well, and are much cheaper to work on. I've always been hoping to find a 27HP to drop in one, but haven't yet. I'm running a 1 1/8" x 4" crank in my one Agco, it was mounted on a Berco snowblower I bought and dropped it into the Agco.

magnumspec.jpg

magnumspec.jpg.2b41238dcc663387df09cf0e186f9a0f.jpg

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