I have recently acquired a craftsman lawnmower walkbehind w/ a honda engine model #917.377790.and it has a feature that allows you todisengage the blade without shutting off the engine.which come sin handy during bag emptying and even starting up.but now it won't disengage and I have to start it with the blade engaged.im getting older now a this feature really helps me out at least to start it easier.I have taken the assy underneath apart and cannot find any problem with it.but I am not sure what I am looking for.any help would greatly appreciated.