ok, but i still have some questions (stemming off of my original Briggs and Stratton post)

why since my engine is 409cc (25cu in.) is it less HP than Bob's 380cc kawasaki? just cause its a kawasaki? ive noticed that many engines have the same displacement but vastly different HP ratings.

ALSO: i know they generally dont get judged by this but...how many HP would a 400cc ATV engine have? how is it different than my B+G? assuming both are 4 stroke...(aparantly my engine has a no load RPM top of 3200RPM's...seems SOOO slow to me...)

the adjustments i can make...(just tell me if i am correct)

1.) ream out carb for more gas flow = more HP
2.) lighter flywheel = more RPM
3.) different air filter = more HP?

thanks again

It's all in how the engine is set up, for hp or tourqe. You can increse the hp any number of ways.IE increse the comp. ratio,larger valves,light wt crank and fly wheel,larger carb-if you go much over stock also change the cam shaft and intake.Then there is always blowers-turbo or roots.It's all in how much hp you want and how deep your pockets are.

Look in the Summit cat. and you will find the jr dragsters, they ar limitted to 5 hp, but that is only for a base line, the Raptur motor is a Brigs and has about 30hp.
some run on metenal.  
I have a catalog some where and will try to find it for you.  The key to hp is compreson.

I just saw a movie called The Fast and the Furius.When ever they wanted more power the driver pushed a red button.Pretty cool!

There are two basic ways to get more power out of an engine.

1)  More work per stroke i.e. bigger cylinder, higher compression, more efficient cylinder filling (turbo/super charging)

2)  More strokes per unit time i.e. higher rpm.

If you have a fixed displacement, the "easiest" way to get more power is to spin the motor faster. Of course the bearings, rings, crank, piston, rod, valves, carbs, exhaust, and cooling will all need to be able to accomodate the higher speed.