G'day smallbear. I'm no expert around here, but I'm pretty sure the other guys will ask for the model / serial numbers and pics if possible so they can give a more detailed answer.
I've had lots of fun and games recently with my ride-on due to a sheared flywheel key after running over a pair of pliers left in long grass. The flywheel being out of alignment threw the timing out, resulting in similar problems to what you described. (It also drained the battery and ended up blowing the con-rod and killing the bloody engine) Could be worth having a look and seeing if your flywheel key is okay.
Have you hit any rocks or hard objects with the blades lately?
Okay, sorry guys, over to the gurus!!
