Cuda4

 I have a Simplicity 10-80 (10hp, 80cm/32" cut) Snowthrower / Snow Blower with a Free-hand control problem. I cannot get the auger control to stay on after engaging it then the drive control. Anyone know how to fix it? I'm  not even sure how it works. The unit is almost 16 years old and has worked well even after much abuse from a stone driveway (and #4 rocks getting stuck in it!). The Free-hand use to work, but it has been years.  I currently use a hose clamp slipped over the handle to hold the auger control down as it takes significant force to keep it down.

Appreciate any input.
Thanks.