A Timberwolf 250 can reach speeds as 55 mph to 60 mph without any modifications to the vehicle's main body. They're not usually built for speed but they can get you from point A to point B.
I think you meant yamaha,as far as i know it goes around 30-35 mph but its speed can be increased upgrading some parts of it which are fairly common in shops.
regards
The Hamaha Timberwolf 250 is rated at 550CC, which is equal to about 150 horsepower. While this sounds like lots of power, you have to remember that this model is quite heavy. The weight will slow it down.