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[Pics] Can anyone tell me about this strange Briggs engine?

Sinister12v

Sinister12v

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Scored a go-cart for free today that was on it's way to the landfill. Now I need a go-cart just as much as any grown man I suppose, but the engine on it was super interesting to me and I had to have it. I'm counting on there being someone that comes across this post that can tell me anything at all about it, as I haven't been able to find out much about it even with having the numbers. The little things I've noticed on it that I'm familiar with lead me to believe it was some sort of racing cart engine from times past, and that it was worth saving just to have. I'm real curious to know if it was worth saving, or if I just hauled someone's junk to my own house

I'll attach the pics..thanks in advance to anyone that may chime in! Fyi, it does run. I was told it had been sitting for a while..and there isn't a breather or filter on it. Assuming rainwater had made it's way into the carb and tank, I pulled those off. Pulled the plug and cleaned it, shot a little spray into the chamber, put the plug back in, and it fired. 20200826_165247.jpg 20200826_165311.jpg 20200826_171059.jpg 20200826_165247.jpg 20200826_165311.jpg 20200826_171059.jpg 20200826_172431.jpg 20200826_213736.jpg 20200826_215631.jpg 20200826_225428.jpg 20200826_225442.jpg
 
Sinister12v

Sinister12v

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looks like a stock engine with some race parts fitted to me ?
aftermarket head, and a race cam probably ?
Hey, don't ask me! Lol. But yes that's something I'm really interested in finding out also. Any guess as to the rating on it? I've seen anywhere from 2 to 5hp on similar looking engines I found on ebay.

I'd like your opinion also on why you think they might have tapped so many barbs into the case? I stuck some spare hose on them in order to keep crap out of it. I figure the single crank case vent is plenty.
 
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frank_

frank_

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those crankcase vents are angled to self draw when driving eh
with the honda gx engines, we used to get double the rated hp by fitting a reground cam and skimming the head about 1/8"
and 6k rpm by deleting the governor
 
aokpops

aokpops

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A 1987 August 21 13 cubic inches about a 5 horse . A flat or L head with a flo jet carburetor no float bowl or float no needle an set way ahead of there time .
 
Sinister12v

Sinister12v

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A 1987 August 21 13 cubic inches about a 5 horse . A flat or L head with a flo jet carburetor no float bowl or float no needle an set way ahead of there time .
Is that carb anything special? Also, do you know what numbers should be on a factory head? Is there any way to before taking it off in order to avoid that if necessary?
 

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Sinister12v

Sinister12v

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Got a few things took care of yesterday. Changed the oil, found a cap to go on the front oil fill that was missing, plugged up those crank vents, cleaned the crud out of the tank, and fixed the exhaust. The upper flange bolt was stripped, I'm assuming that's why some idiot had wrapped a bunch of steel wool and crap around it as you can see in the first pictures I posted. Went up to a 5/16-28 and found an allen head to go in it.


Hopefully be able to ride it around by tomorrow evening. Last major thing I need to do is figure out how I'm going to run the throttle cable. Most little flatheads I've seen have that mount on top of the head but the geometry just doesn't seem right to me. I don't think that pulling from a 45* angle downward on a lever that's supposed to only move laterally is gonna get it done. Any info on that would be greatly appreciated.
 

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aokpops

aokpops

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Is that carb anything special? Also, do you know what numbers should be on a factory head? Is there any way to before taking it off in order to avoid that if necessary?
The carburetor is nothing special but are a surprise to watch . A light bulb moment when you see it work . The factory head is flat and know nothing about head numbers. I can’t believe the head would be anything special being a flat head. I seen people make heads out plexiglass to see the combustion of the engine.
 
Sinister12v

Sinister12v

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Little update if anyone might be interested. Got it running the other day, it fired right up on the second pull. Took it for a stroll up the driveway and holy crap, it went every bit as fast as I wanted it to, and then some. Sat it back on jack stands and thought I just needed to run a kill switch and that'd be all. Well after that was done my pops came by and I cranked it up to show him, when we noticed some oil coming from where it shouldn't. Got some bad news after pulling the head. Whoever owned it didn't keep oil in it...as the cylinder walls are scored. I'm really hoping I can hone it out and throw a set of rings at it along with a new gasket and be okay. May just be wishful thinking though. Check out those valve springs and the head work..
B1.jpg B2.jpg B3.jpg B5.jpg B7.jpg B8.jpg B9.jpg
 
Sinister12v

Sinister12v

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View attachment BriggsRunning.mov
dual spring eh, they must have had that revving to 8k
oversize valves ? hows that cam profile look ?
I'm going to pop the case open soon as the sun comes up good, and I'll post up pictures of what's inside. Since looking under the valve cover I've been anxious to see what's in there. You reckon those are bigger valves by the way? I noticed the pin-punching around the intake valve seat, I just didn't know what the diameter of the factory valves were.

Did measure the head gasket so I could get a replacement ordered. It was somewhere around .055-.060.
 
anlrolfe

anlrolfe

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Lap the valves and check the clearance(to cam) especially on the exhaust side.

My Generac 2400 gen-set has the same series of engine but not modded like this.
These are simple, rugged, workhorses, parts are plentiful used widely on garden tillers, snow blowers, gen-sets, pumps, compressors.
Not sure how they compare for power/efficiency with new OHV designs.
I suspect the new designs makes manufacturing faster and cheaper.
 
frank_

frank_

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definitely looks like an aftermarket head to me, with those oversize fins on the exh side
and the centre punching is probably to help stop the thinner valve seat from lifting eh
 
Sinister12v

Sinister12v

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definitely looks like an aftermarket head to me, with those oversize fins on the exh side
and the centre punching is probably to help stop the thinner valve seat from lifting eh
Head has both a 12 and a 13 on the underside. Would like to know myself. Trying to determine the best route forward.

Need to check and true the bore first of all I'd say. Just popped in to print some specs so I can go back out and measure the bore, to see if its got any wiggle room to bore still.
 
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