The WR450 comes from the factory choked up and with very little power so that it's almost an embarrassment to ride. And why would the factory do that you may ask ? And the answer is..... California.
In order to sell a Yamaha WR 450 in California it has to pass very strict tests for pollution control and noise reduction so Yamaha does things to the engine so that it will pass these very strict tests and they can sell the motorcycle in California. California is a very big market so the politicians there can get businesses to do just about anything they want, whether it's good or bad or right or wrong doesn't matter.
But Yamaha is smart enough to know that nobody in their right mind would buy a 450 cc motorcycle that runs like a 250 cc motorcycle so they make these changes to the engine reversible. One of the things Yamaha does is put a screw in the throttle cable mechanism that only allows the throttle to open up about halfway. A simple way to envision this is if you put a small block of wood under the gas pedal of your car so that instead of the gas pedal going all the way to the floor it would only go down about an inch. if You did that your car would get better gas mileage, it would pollute the air a lot less, it wouldn't make as much noise, the state of California would love you, but it would only go 35 miles an hour, and take a looong time to get to that speed. So today I took that accursed screw out of the Yamaha and threw it as far as I could.
Another thing Yamaha did to make California happy was to partially block up the exhaust pipe. They do this so the engine can't breathe properly and therefore the engine produces less power, less power equals less noise. This was a little more difficult to fix but it still only took half an hour.
The tiny little pipe in the middle is nicknamed the "pea shooter"and it's only job is to make the Yamaha WR450 run worse.
I took the cap off of the muffler and pulled out this part that has the pea shooter riveted into it
I drilled out the aluminum pop rivet
The black thing on the left is the "pea shooter"after you drill out the rivet you can easily pull it out.
No more choked up exhaust pipe.
There's still a couple more things I'd like to do to turn it into a normal motorcycle but the two things I did today are biggies and make the WR450 run a lot better.