It sounds like you either have broken linkage or a bad clutch.  If the linkage is not broken then check out the clutch brake adjustment.

Page 2, section 4a in this pdf file link tells how to properly adjust a typical clutch.  Always adjust the clutch brake first and then the linkage.  Be sure to have someone hold the clutch down - engine not running, of course - or block the clutch down before trying to adjust the kwik adjusting nut.  Otherwise you may break the teeth off the inside and not get the adjusting ring to turn.