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 Briggs 12.5 flathead Question

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WilliesBuilds
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PostSubject: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeOctober 31st 2013, 1:16 pm

ive got a 12.5 flathead off a murray widebody and I would like to give it a good tune up . what are some mods i can also do ?
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cumminsbayou
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeOctober 31st 2013, 3:49 pm

It really all just depends on how much cash you wanna spend. Easy mods would be like throw a 11hp head on it, copper head gasket, carb to like a 13hp and up briggs, better air filter, straight pipe exhaust, and port a polish the valves. That should make it at least 13-14hp i'd think. If you really wanna get in to it remove the governor on it to and put a exhaust spring on the intake side of the engine.
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willis923
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeOctober 31st 2013, 4:11 pm

for just a regular tuneup, id put an NGK plug in, use quaker state 10-w30 oil, fuel filter, air filter.. them from there, you could remove the governor, port/polish the heads, decarbonize everything, lap&adjust your valves, get an exhaust spring for the intake valve, straightpipe stack or sidepipe..
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WilliesBuilds
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 8:27 am

that all sounds really good . I is there anywhere I could find more info on what is porting and lapping the the valves? don't know too much about that
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willis923
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 8:29 am

there is most likely a few threads in the engine tech section. i can look around in a few hours when i get home from school, or you can do it if you'd like.. i know there is something on the topic though
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cumminsbayou
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 8:52 am

WilliesBuilds wrote:
that  all sounds really good . I is there anywhere I could find more info on what is porting and lapping the the valves? don't know too much about that
Try looking it up on youtube
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 11:10 am

Maybe a after market air filter, let it breathe better. Straight pipe, maybe 2" and at least 2 1/2 feet long. Change oil, and for more power Pitt and polish the intakes, that along with what cummins said.
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WilliesBuilds
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 11:45 am

i will be doing that soon then lol
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TroyBilt Pony
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 1:09 pm

Ill tell you how to build lots of power out of these.. more than you will usually ever need..I'm at school so ill type it up when I get home.
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redlinemotorsportts
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 2:47 pm

TroyBilt Pony wrote:
Ill tell you how to build lots of power out of these.. more than you will usually ever need..I'm at school so ill type it up when I get home.
He just wanted a tune up, not a $1,000 racing engine build lol
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 3:31 pm

He also said whats some mods.. I'm not planning on buying much.. I'm just saying free stuff to do at home
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WilliesBuilds
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 3:54 pm

sounds good man ill be waiting for that cheers 
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitimeNovember 1st 2013, 7:04 pm

Here are some cheap upgrades you can do to your 12hp to build more..
None of these are in order, although some should be done at the same time
Durability
~OHV Rod, rods out of a 14.5 horsepower ohv are known for handling higher rpms.
~Billet Aluminum Counter weight link, know to break under ungoverned condition.
~While you have your engine apart, check out your cam lobs, crank/cam gears, and lifters. If all is good, reinstall with some motor oil on the sliding parts.
~If your crank has a nut on top, swap to bolt.. its stronger. I run a nut and its fine. But bolts are always stronger.

Power, this can get pricey, depending on what your want out of your motor.
I'll get the cheap stuff out of the way.
~Port & Polish, better flow = better performance. Some people like to leave the intake a little rough. I personally like both intake and exhaust smooth as possible.
~Shave Brows on block = Helps with flow and compression.
~Shave the head 0.20 = more compression, some will argue this as most think everything is flow. While Flow is extremely important, compression is torque.
~Dual valve springs, or put another exhaust spring on the intake, which isn't much of a difference. But better than nothing.
~Decarbonize everything. If your aren't lapping valves, dont mess with them. Easy way to cause a leak. I personally like to use a gasket scraper to clean the head then sand with 500 grit.
~E3 Spark plug,  some like em, some don't. You decide.
~+4 degree timing key, Dont expect to run lower idle smoothly. But higher rpms, you'll be cooking.
~You want to have a tach, keep rpms below 5-5.5k..Can be bought on ebay for 15 bucks for a cheapy.

Now we will get expensive.
SS Valves, Custom Cam, ARC Flywheel, Dual Valve springs, Billet lifters, Billet spring retainers, get her bored out .30, Custom carb by ec.. that will get you scooting.. there is more, but I cant release all of my secrets Very Happy
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PostSubject: Re: Briggs 12.5 flathead Question   Briggs 12.5 flathead Question Icon_minitime

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