Spray paint honda rebel tank?

How many spray cans of paint would it take to paint a honda rebel 250 tank?

That will depend entirely on how many coats of paint you intend to give the tank, won't it?

Use two cans depending on the size of the can. Spray paint isn't the best and you'll need a thickness you can rub back and polish without wearing through to the primer.

You can repaint it with one can adequately, even if there's a color change.