I need some help with the maintenance of my Exmark 48 walk behind. This just started on the last property I mowed last week. When I push the lever down to engage the blades, the lever does not stay locked down. It pops up and the blades disengage. Ive looked at the mower and cant figure out how to adjust the lever. Im not a mechanic and I usually take all problems to my dealer. But, hes 45 minutes away and I wont be in his area for at least another week. Can anybody help?