Worth to rebuild an old opposed twin?

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Jun 1, 2013
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Albany, NY
I have one of those 46 series opposed Briggs, about 20 years old. It ran well (bit of smoke on startup) until it threw a rod (spun top bearing). Both rods broken. Maybe I didn't check the oil, maybe just 20 years of use and it had it.

There are very few parts available.

Crankshaft has some aluminum tracking on the journal, some say it could be cleaned with oven cleaner (I could post pics). Guess it could be machined, but I don't see parts for a machined crankshaft. The measurements on the journal mics out. (other one still has part of the rod on it)

I would buy a new one but the reviews on the newer mowers are terrible.

I would need at least rods, possibly pistons and rings (they seem ok, but I would have to take apart more). Lots of shrapnel in the crankcase.
 
Joined
Jul 14, 2020
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Well, if you are going to replace the rods, which is obvious that it needs, you will have to take the pistons out also, so I don't see how you would have to take apart more. I have always cleaned the aluminum from the crankshaft with emery cloth. My guess is that it was LOW on oil. Pistons and cylinder walls may be scored also. Is it an all aluminum block, or is it cast iron lined??
 
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Apr 15, 2010
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Connecticut
I love the way they sound, but those old opposed Briggs just eat fuel for how much power they make. It will be easier trying to source a good used one than trying to find parts. If there is all sorts of metal inside the block it might not even be good enough to use.
 

ford46guy

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Jun 1, 2013
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Albany, NY
Well, if you are going to replace the rods, which is obvious that it needs, you will have to take the pistons out also, so I don't see how you would have to take apart more. I have always cleaned the aluminum from the crankshaft with emery cloth. My guess is that it was LOW on oil. Pistons and cylinder walls may be scored also. Is it an all aluminum block, or is it cast iron lined??
Says commercial cast iron sleeve. I admit I got careless checking the oil. I kinda figured it is old and ready to go any day. My neighbor is an old mechanic, he said they never blow with good oil. He saw the damage inside, he said it may be salvageable, 50/50.

Probably going to tear it down, but it looked ok thru the inspection hole (no major gouges). Anything new that size is $800, might as well get a new tractor. I don't know where to get a used one.
 
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Jan 22, 2011
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Scrap it. With all the debris, you will kilely have to replace everything. Not worth it. I am surprise a rod didn't go through the block.
 
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Ottumwa, Iowa
You see those old motors for sale every now and then but might just cost as much to find an identical model for parts.

It all depends on how much you like it.
 

JTK

Joined
Aug 14, 2003
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14,911
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Buffalo, NY
I love the way they sound, but those old opposed Briggs just eat fuel for how much power they make. It will be easier trying to source a good used one than trying to find parts. If there is all sorts of metal inside the block it might not even be good enough to use.

Agreed.

The sound is the only good thing these engines offered IMO.

I'd only rebuild it if it was a collectors item restoration project.
 
Joined
Apr 7, 2019
Messages
490
Location
VA
This guy did a rebuild however I would've replaced both pistons, rings, and the rods if I was getting that far into it. These engines are fairly bulletproof, mostly the common issues are the carb, coil, and the upper piston is usually the one that goes out first due to being splash lubed and the lack of lubrication that reaches it.



The one I have has been pretty good, I bought the whole mower for $275 and only needed to clean the battery connections, previous owner installed a battery from Tractor Supply that had the round terminals and used adapters to convert it over but were painted, I used a file and sandpaper to clean both sides and that's all it needed to get it running. Evidently it was an engine swap from a Craftsman and the wiring was different so I took it to a shop that got it resolved and to fix the charging they needed to add a diode. They worked on the carb but don't really know why and seemed to be fine but they incorrectly installed the linkage and said it was ready to pick up but clearly wasn't. I found someone on eBay who sonic cleans and rebuilds them and while researching the carb online I found pictures of the linkage and discovered their mistake so I fixed that when I reinstalled the carb.
 
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