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SmilinSam

Sunstar engine mounts

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SmilinSam

Whats the difference between single cylinder engine mounts on a Sunstar and Opposed twin engine mounts in a Sunstar?

Whats the difference between those and the V-twin mounts?

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huffy

Both the opposed twin (Magnum) and V-twin (Command) mount to a plate on the frame. See pics from the manuals below. There are only 2 differences, really. The first is that the Magnum has a much larger bolt pattern than the Command. So, if you're switching from one to the other you've got to drill new holes in the plate (the Command holes also have to sit farther back, if I remember right, so that the PTO pulleys line up). The second is that, as Bob pointed out, the Magnum has some rubber washers between the motor and the plate, whereas the Command doesn't. I think that's because the Command is much smoother running and, thus, doesn't need them to quell the vibrations.Magnum mounting:

Magnum mounting.jpg

Command mounting:

Command mounting plate.jpg

Command mounting.jpg

57e0615492fb5_Magnummounting.jpg.9d243f24263fe7f0114fcbd63a6eab2b.jpg

57e061549ef08_Commandmountingplate.jpg.0fe7949e010bd68c2ecb863074d43bc5.jpg

57e0615591efa_Commandmounting.jpg.9b6499278dc8014f4517f0c85fdba539.jpg

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SmilinSam

So, if I ever wanted to go from a single cylinder to a twin I would have to find a plate to put in the frame?

From the diagrams above it looks to be a bolt in plate. Is that right?

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huffy

Sam:

My guess would be that all versions they made had the engine bolting to a plate. I don't see how the single cylinders could have not had one, as without the plate there's nothing to mount the motor to.

Yes, it's a bolt in plate. You bolt the engine to the plate, then the plate bolts in between the frame rails.

I had some pics somewhere from when I switched from a Magnum to a Command, but I can't find them right now. I'll look on my other computer when I get home.

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SmilinSam

My single cylinder has a plate welded into the frame, the engine is bolted to rubber iso mounts which are bolted onto that plate.

My confusion stems from a few different factors.

#1 Al Eden had said(I think)at one time that his repower kits would not work with the single cylinder tractors as the mounting plate setup was different. Could be wrong, but I think that's what he had said, and he's no longer with us to clarify.

#2 My tractor in question has a single cylinder in it, and was a yard dog at the Simplicity plant as per another club members history of it who did own it before I got it. It was said to have blown the engine in the test lane and was repowered as a yard dog there at the plant.

#3 However, when I run the mfg # on the tractor it comes up a 18hp twin with manual steering.

Just trying to figure out what I can use in this down the road whgen this engine bites it.

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GLPointon

Thanks for the topic Sam. I had no idea of the diff. mounts.

One of my 1918's has a blown engine & I thought I could just drop in a Kohler 16hp if I wanted...evidently not XX(

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BLT

The early Sunstars had 14 & 16 HP single cyl Magnums. Here is the 1988 line up:

Model***********HP**Product***Mod****Spec

SunStar**G.T.***20**1691381***M20****49544**

SunStar PS G.T. 18 1691528 M18 24566**

SunStar MS G.T. 18 1691380 M18 24566**

SunStar G.T. 16 1691357 M16S PS-711521**

SunStar G.T 14 1691250 M14S PS-601538

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GrincheyOne

The older machines 9FDTs) had what was called a "front weight plate" and

is mounted on the underside of the frame. It is held in place by the bolts for the engine, and the bolts through the foot rest assy.

I'll have to see, if this would fit inside the frame. the front support block, and the rearward support angle also bolt through this 'plate".

The one from my '88 2110 is "gulled' out from the front support block being a bit loose over time, and stressed by being the main support for the front axle assy. It is 1/2" thick, and weighs in around 17#.

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huffy

Sam:

When I switched from the Magnum to the Command, all I had to do was drill new mounting holes. I did not have to otherwise mess with the plate, as the distance from the bottom of the motor to the center of the pto shaft was the same on both motors; that is, the mounting plate did not need to be moved up or down. I think that will be your biggest concern in finding a replacement motor. Of course, a slight variation up or down can be solved simply by using longer or shorter pto belts rather than moving the plate.

Another issue that I had was that the Magnum and Command use different electric pto's. To get the pulleys correctly lined up I had to move the Command a bit farther forward, which necessitated me lengthening the drive shaft about 1-1/4". That was easy, though.

I also had to reroute the exhaust because the mufflers are different, and swap out the choke and throttle cables because the Command models needed longer ones.

Greg: between the single cylinders, Magnums, Commands, and Briggs set ups, there were several variations. Swapping the motors themselves isn't hard at all. It's compensating for the variations in pto's, drive shaft lengths, throttle and choke cables, and mufflers that's hard. Well, not really hard, but it requires hunting down some parts and fabbing others.

Oh, yeah, and the wiring on a Sunstar is a confusing mess. Just ask Josh. We've both had to have Bob Tiarks 'splain that to us. It is utterly beyond my comprehension.

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Brettw

I would also add, that the opposed twins (Magnum's), the mounting holes are drilled at about 3/4". You do need the rubber motor mounts that make up the difference between a 3/4" hole and 9/16" motor mount bolt. The rubber motor mounts do that. I have no idea if the same holds true for Commands, or singles, etc.

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