I used to run my Uncle's Graham Bradley at about 35 mph. That is movin right along. Thirteen years old taking my cousins 3 miles to town for a movie. Fun tractor to drive down the gravel and dirt roads past Grandma's house. /forums/images/graemlins/wink.gif
Don't know about the new Deere, but in my youth the 2cyl Deere were not too fast compared to some of the others. But I wouldn't doubt 25 mph on the new ones.