# ebay Briggs 18hp opposed twin...



## TecumsehBriggs (Jun 17, 2011)

Won the bid on a Briggs 18hp opposed twin on ebay. Final bid was $5.50! Of course the shipping was $99, but came all the way from northwest Wisconsin to Naperville, Illinois. The seller wouldn't allow me to pick it up for such a low price. That's ok, because I didn't want to drive hundreds of miles to pick it up!

Arrived today around 11 am.

Took it out of the box; it was on its side inside a plastic tub, inside a couple boxes. Cut a hole in my outside workbench with an air chisel to make a test fixture. Set the engine on the bench, shaft in the hole. Took off the tins; replaced the starter, flywheel & charging ring with spare parts in my inventory; replaced the fuel line; hooked up a fuel tank & a battery. 

This thing started right up! Took a little while for all the oil to burn out of the muffler, but when it did, WOW! What a smooth, quiet engine. So, I guess I did ok for $5.50 (plus shipping).

I ws going to put it on a tractor I have to sell, but it runs so well I may put it on my beloved Ranch King! The 16hp ovh Tecumseh runs well, but a Briggs 18hp opposed twin is WAY better!


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## jc56 (Jan 16, 2012)

You know I had one of those on an old MTD a few years back.I mowed with that mower about 15 years before the deck got totally fried...lol......then took the deck off and gave it to my stepson to ride around on for a few years.He let it sit and we just junked the whole thing. No telling how long it would have ran.But I'll tell ya.....it was the "smooooooothest" running engine I have ever seen.You got a great buy man.Good luck with it!!!!!!!jc


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## jhngardner367 (Apr 5, 2011)

The twin I put on "Frankenwheels" is nearly 30yrs old,and still runs great! Those engines,I think,are better than the v-twins,by far.


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## TecumsehBriggs (Jun 17, 2011)

I agree, I love the opposed twins. A small engine mechanic/shop owner I know hates them, calling them the worst design Briggs ever made. I don't believe that at all. Keep them full of clean oil & blow out the mice nests every once in awhile!

I now have one 14 hp & two 18hp opposed twins awaiting reassignment. I have 3 mtd tractors with 18hp opposed twins awaiting restoration & a few others as well. I prefer the opposed twins over the ohv any day!


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## jhngardner367 (Apr 5, 2011)

The great thing about them,that many people DON'T know,is that it's easy to convert a horizontal twin,to a vertical,and vice-versa,because the parts,aside from intakes,sumps,back plates are the same!


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## Ed G. (Apr 25, 2008)

I got mine for cheap from a friend who was cleaning up his yard and it still had a Dynamark 18/42 attached.  It gave me fits with poor performance under load till I finally bit the bullet after the starter gear lost all its teeth from having to restart it so often. Since I had it apart, I stripped down the carburetor and found a lot of crud in there. I managed to salvage the old gaskets, but I did spring for a fuel pump rebuild kit. Carbs aren't my strong suite, so I resisted going in there till the bitter end. I don't know why I was so worried, disassembly and cleaning of the carb was a cakewalk.

I was a bit surprised to see how many engine parts are still available online at Partstree. Just wish I could say the same for the Dynamark and its MIA mower deck. So no mowing duties, but it sees a lot of use hauling trailer loads around the property.

Anyway, it's a great engine and other than all the covers and shrouds, really quite easy to work on.

-Ed


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## maxoverload (May 6, 2017)

Old thread but my 2cents - still have my dynamark 18/42 - with the same cast iron granny gear 5 spd that some JD/Cub tractors came with - recently found a nos b&s horizontal 18hp - but my dynamark is a vertical - could not help but notice the comment by jhngardner about ease of converting them - I hope someone can give me the guidance and vitals for the procedure


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## jhngardner367 (Apr 5, 2011)

Here you go,fellas !
SPECIAL NOTE: THIS DOES NOT WORK ON ENGINES WITH BALL-BEARING CRANKSHAFTS!!!

Remove the intake,and controls(save all parts you remove).
Drain the oil,and remove the sump ,and end plate .
Use the PTO cover,,and the sump ,from a horizontal on the vertical.
Before installing them,however there are a couple of mods,to do .
1)check the position of the connecting rod oil holes. #1 has the oil hole facing TOWARDS the cam gear,and the oil hole in #2 faces AWAY from the cam gear .
2) Install a dipper from a horizontal engine( p/n222480) on #1 rod( see picture).
Remove the splash tray,(if equipped)from the sump,as it's no longer needed .
3) Check for a flat pad,on the block of the vertical engine.
This is where the dipstick will go(All twins have it).
Center punch the pad,making sure it is CENTERED,then,using a 1/2" drill bit(a long one), drill through,to the open crankcase(MAKE SURE the bit stays on a 90° angle .to the pad!)
4) use a 59/64" drill bit(15/16" if you don't have a 59/64"),and enlarge the hole(from the pad) to a depth of 1& 1/4".
Use a 3/4 NPT pipe tap,and tap threads in the first inch.
This is for the rubber,thread -in grommet,for the dipstick tube .
Clean out all shavings/chips thoroughly .
Install the horizontal sump,and use a pipe plug on the hole ,where the vertical dipstick was.
Use the intake from a horizontal,as well as the controls,and breather tubes,and exhausts ,and shrouds.
This should complete the conversion.


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## maxoverload (May 6, 2017)

Yes sss , this I can do - but need ask - with motor in vertical orientation - looking at carb - which one is cyl #1 ? - thanks - regards Leo


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## jhngardner367 (Apr 5, 2011)

There are cylinder numbers on the block,but if the out put shaft is facing you ,#1 is on the right(over the starter).
on a vertical,if the controls,and exhaust are toward you,it's on the right.
Note that the flat,for the oil dipstick tube is also on the right.


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