more rpms from a briggs 12hp flathead

so recently I've been researching on how to get just a little more rpm outta my Briggs, so i came across removing the governor  and all it's weights, purchasing an OHV rod, and getting a billet dog bone for the crank weights, this supposedly should make it 10x safer then just turning the piss outta it, the rod and cranks weights would still be a problem correct? what are your guys thoughts on this??

they said to port and polish, use and exhaust spring on the intake, grab a model 28 ohv rod #494504s, a billet dog bone for the crank weights and removing the governor

i would also be running a strait pipe and k&n filter and possibly a 11hp head although higher compression would put more stress on the rod, maybe that wouldn't be advisable?

I generally caution people against valve spring upgrades when running a mostly stock engine ungoverned. Valve flutter serves as a failsafe against higher revs breaking stuff. While the OHV rod is purportedly a little stronger, it's still a stock conrod.

Grab yourself a fresh coffee (or your own favourite bevvy)- and read this: https://www.atltf.com/t2575-governors-flywheels-and-an-internet-full-of-crap

haha i read that numerous times! i just wanna be able to rev it without sending a rod through the block i mean a stock rod won't do too much, but seems so much beefier then the stock flattie rod.

at least from what i read from what i read the dogbone snaps and there goes the weights. that's why i wanted a billet dogbone.

i know all the will cause more wear and destruction won't be prevented, just looking for some cheaper options then billet this and that that will still make if a little bit safer, if i can spend 20 on an ohv rod and run it like that i'd much rather do that then spend $130 on a billet rod, lol i'm a high schooler that wants performance on the cheap

After doing valve and internals. ARC Billet flywheel is required in my book. These 12hp flattys can be built to turn 8-10k rpm. At that rate. Cast Flywheels can explode.

To heck with the flywheel. If you're trying to turn 10K, you'd better not have ANY factory stock parts inside!

Doc Sprocket wrote:

To heck with the flywheel. If you're trying to turn 10K, you'd better not have ANY factory stock parts inside!

Heard that! Sounds like a $1K+ engine to me if your turning that much!

WARP SPEEEEED!!!

i just wanna be able to get 5500 outta it, mabye 6k lol that might throw a rod lol

murrayracer wrote:

i just wanna be able to get 5500 outta it, mabye 6k lol that might throw a rod lol

by the time you will be done, all that will be left is the block. rest is aftermarket/custom

xxXMowerdudeXxx wrote:

murrayracer wrote:

i just wanna be able to get 5500 outta it, mabye 6k lol that might throw a rod lol

by the time you will be done, all that will be left is the block. rest is aftermarket/custom

md don't falsely inform someone if you don't inow what your talking about.
I rebuilt my 12hp 2months ago. Ungoverned it turned 5100 at most. That's with some port polishin, shaved brows, cam timing adjustment, new e3 plug, thin headgasket, ohv rod, and synthetic 5w 30. I also did some carb work. I also had some valve springs from a pressure washer pump that were really stong so for ***** and giggles.. I put them in and tached it. It hit 6200. I quickly swapped back fout for stock as my engine isnt prepped for beyond 5k. So get your basics done first.

so i wanna hook up a tach can i use a 4,6,8 cylinder? will it be way off? like this http://www.harborfreight.com/automotive-motorcycle/dash-gauges/2-inch-led-lit-tachometer-98480.html

or would a scooter tach work? not preferable seeing as it's 13k rpm
http://www.ebay.com/itm/A-S0-Universal-Motorcycle-Scooter-13000RPM-Analog-Tachometer-Gauge-Night-Light-/301003517023?pt=LH_DefaultDomain_0&hash=item4615352c5f

A tach for a powered coil (standard) ignition won't work on a magneto-driven engine. A popular choice for engines like ours is the Tiny Tach http://www.tinytach.com/ They are relatively cheap (EvilBay) but many don't like them because they are digital.

There are tachs out there that work with magneto-driven outboards, but they'll likely cost you. Aftermarket diesel tachs can work too, because they do not rely on the ignition system (go figure).

hmmm, well, i don't care for the tiny tach because the refresh is only every 2secs? i would love to have a analog tach but not have to spend the huge $$$ so i was research and found that you may be able to place a diode and be able to run it as a single cylinder

Here ya go! http://www.instructables.com/id/Automobile-Tachometer-on-an-outboard/

thanks Doc!

You're welcome. I had to do a bit of searching- you jogged my memory with your comments, I knew I'd seen it before somewhere... On DIYGK. I may have to try this- I got a nice 4" tach would look GREAT on one of my rides!

tell me how it goes! i might get around to trying it one of these days!

Equus makes a tach that has a button on the back that you push to set up ( not the 4,6,8 ) this button can set it to work with 1 all the way to 12 cyl. The tach is the 68 brand. (6068, 7068, 8068) its not too expencive. Canadian tire has them in Canada and im sure most places in the states will sell them for around $50 for the 6000 series. Equus is pretty popular so ordering one from a parts type place wont be a headach!

As for engine mods. I love cheaps mods/improvments so your in luck!  

I always like to lap the valves when i get a reason to take the head off. Most of the engines ive taken apart end up having the start of pitted valve seats due to a few reasons like engine hot spots and maby even sitting for awhile (rust starts to form) a valve lapping stick and compund is cheap. Any parts store will have some. Just make sure you check valve lash after. Look up some tutorials on it. I have one ony youtube channel ill post.

Another thing i might replace is the fuel filter. A pluged up one can give you a head ach when its runnin rough wide open with a clean carb!


A hotter plug will also do you good in your adventure to gain some extra power. I like to use a 9 heat range Champion spark plug with a gap of .035


Good luck! :-P