Has anyone ever thought about performencing your engine? I would like to do it. Like put a k&n filter and such what are your thoughts? Also is thier an easy way to make an engine have more hp besides removing govenour?

You can buy K&N filters for the motor practically anywhere - briggs motors dont like polished intakes - removing the governer is at your own risk - its there for a reason. Only proper way to do it is to have the engine properly built with a billet flywheel .

Again, best bet is to get a larger displacement motor.

The flatheads like the eyebrows shaved don't they? I've been thinking about doing it to both cylinders on my opposed twin sometime down the road.

Im not sure internally , ive herd briggs need the rough texture in the intake to run correctly - im sure just port matching and cleaning the head would work.

I cant remember if it was using a 10HP flathead head on a 11-12HP flathead motor- itd give it more compression ( those are all the same motor).

I belive an 11 or 10hp on a 12hp engine yes. I read somehting about that a while ago.
Could always skim the head.

Anyone able to tell me more about shaving the eyebrows? Alot of people do it but im not sure exactly what it is.

Being such small engines, there isnt alot you can do. Without spending lots of money on billet flywheels, rods, pistons, all that stuff. With these you can safely run a higher rpm, that's where you'll get the most power gain, but on a standard engine I'd highly recommend not to do it.

Chunk: yeah i herd something about all the briggs flatheads from like 10-13HP are virtually the same ( which is weird because how can they determine additional output HP?)

From what i gather, most racers use 12HP and up motors , depending on what class they run depends how modifed they are . Once mods are performed , a billet flywheel IS a must- stock cast flywheels spun over stock top rpm of 3,600 rpms will eventually fatigue and explode . I say by the time you dump several thousand into a smaller motor, itd be cheeper to just get a larger motor.

A guy i used to work with used to have a 8HP wheelhorse tractor he modded for tractor pulling - he said he dumped around $8000 into prepping the motor alone.

When you get into OHV motors, its actually easier to mod those, with roller rockers, different valves, valve spring rates.

I seem to find L-heads to be tuffer though.
I have one 12.5 i/c brinng that i ran all the time with no governor on my old monster mower and it still runs fine to this day.

The difference between 10-11-12-13HP is basically the stroke length, and crank travel, longer block = bigger HP. But otherwise they are basically identical. I've never heard about using a 10HP head on a bigger motor, Are they really different? I'd like to find out

10HP heads give more compression - i think its cause the bowl is smaller.

I cringe when people remove governers- stock motors are only good for 3600rpms - any higher and it needs to be modded .
Ive seen pics of exploded cast flywheels - one exploded and pieces flew several hundred feet into the side of a steel barn and carved its way into a steel support beam- the guy standing next to it had his leg severely torn up when it let loose.

Id say at least make a new flywheel shroud with 1/4" steel plates or get a billet flywheel- $150-200 for a new flywheel is worth not getting maimed or killed over.

I figure if you cant get more power from a small motor easily ( w/o removing the govnah ) - go for more cubic inches.

See.., i believe in making as much power as possible with the least amount of displacement.
But yeah as for small engines, it is cheaper just to drop a twin cylider in it.
The 10hp heads are a great cheap mod though, i've only removed the governor on two engines is my life and don't run them much higher then 4300rpm's.
I have a small engine tachometer so i can tell how high they reving.

Will any of the heads off the single cylinder engines fit on the opposed twin? Maybe bump the compression by swapping a couple of them onto mine?

I figured it was a long shot. Though the way they build things interchangeable, thought I'd at least ask.

Singles are nearly all interchangeable ( older ones ) - twins are a different animal altogether . In the late 90's they started changing carbs and stuff ( early models had the single piece carb- later ones have the intake and air cleaner separate from the carb). Multiple piece carbs wont bolt up to motors with the single carb- different bolt location- i suppose if an adapter was made itd work tho.

I do know a 14.5HP OHV single rod will fit the 12.5HP singles- the 90's 'power built' 12.5 rods are junk. Ive gotten 3 of those motors all with shattered rods.