Did you forget to clean out your lawn mower deck before putting it away for the winter? Do you now have grass clippings stuck to the underside of your mower like cement? This will help speed removal of grass.
Help clean your lawnmower deck of dried grass by idling it for a few minutes or so while spraying water under the blade. This will force feed the water into the hard grass and quickly soften it up.
Just use a putty knife or even a piece of wood and scrape the remaining softened grass from under your mower deck. After shutting it down first of course.