Re: Looks good but is slow...
sounds like it's running rich. closing the petcock leans it out as it burns the fuel. where's your needle-clip set? try moving the clip up a notch and see what happens. if it goes faster, check your plug. if the plug is still black, oily, or dark brown, go up another notch. you want the plug cocoa colored. any lighter and you're too lean.
oh, and i forgot to tell you to check your plug before you move the clip. if it's already light tan, then you got a slow motor, and we'll have to figure something else out.
and, what mixture are you running? you should be at 32:1 after that many miles. if you're running it with more oil than that, it's too rich.