Far as mods for "Free Power",,
1) Do the "CAM TIMING MOD"
that makes a Large change.
(Google it,,,a buncha places have instructions with pictures,etc)
2)Remove air filter lid
3)Remove the Spark Arrestor in the Exhaust
4) Advance the ignition timing a LITTLE
You MUST rejet the thing.
Figure about $20
You NEED to use premium quality Synthetic Oil,,,thats a few $$$
It'd be WISE to use a NGK IRIDIUM plug,,,about $10
As-Is ,,,your 450 makes about 40HP @ 8,000.
Power falls drastically after that---engine just runs out of breath
By 10,000 it's about 28 hp
The above listed Mods will raise it to about 50HP.
But Far more importantly,,,it fattens the power curve AFTER the stock 8,000rpm Peak.
Power falls off far,far less and much "slower"
It will actually Pull all the way to over 10,000 rpm.
And make as much power over 10,000 as it does Now,,MAX.
An approx 25% gain in Power,,,
at an approx 25% Higher RPM,,,,
WILL put an end to your complaining about "Not Fast enough"
Your stock motor Suffocates,,,and cannot even wind-out Hi Gear.
And just piddle-farts around ,,,slowly revving out the lower gears as it power falls like a rock.
Basically "Over Revving" beyond it's Peak
The above mods will make it BEHAVE like a real Race Engine.
It will pull Strong until it quits revving.
How well you TUNE it,,,ie Jetting and Ignition Timing,,,will determine Total HP Number.
You can find How-To's allllllll over the internet on each mod.
It'll outperform $500~1,000 worth of Bolt-On crap.
And it does NOT really bother the engine at all.
Those motors are set -up sorta odd , originally.
It's almost a a form of restriction.
The Mods,,,set everything closer to "Optimum",,,
or how Yamaha COULD-HAVE chosen to set it up.
So it's no freaky,oddball stressful Hop Up Hatchet job.
Not a bad deal,,,for "Free"
Lastly,,and NOT Free,,,
get 2 countershaft sprockets.
1 tooth Larger than stock,,
1 tooth Smaller than stock.
Your motor will NOT rev to it's Max RPM in stock form.
After the Mods,,,it WILL.
A SMALLER front Sprocket ,,,,with the extra RPM's from the Mods,,,will go FASTER top speed,,,,but also have Much Greater acceleration when pulling thru the gears.
The 1 tooth Larger,,,will go a lot Faster top speed,,because the engine can pull it to a much higher rpm than the stock motor can
Gearing is optional,,,,having the Stock gear,,and a +1 & -1 gives you a Bunch of flexibility to dial it in for Where & How you ride.