BX MMM height control knob

[rlw]

The last few times while mowing, I've looked down at the height adjustment knob and noticed that it has changed to a lower setting from what I started at. My yard is fairly bumpy and I assume that the bouncing around of the deck is causing the height adjustment to move. After the first time it happened (and scalping the lawn), I tightened the hydraulic knob so that if it happened again, at least the deck wouldn't lower.
I haven't had time to investigate how the height control knob actually works and why it might be automatically moving. Thought I would see if anyone else has had this happen or if anyone had any ideas.
Before anyone says Slow Down - I actually mow pretty slow due to the bumpiness and to get a decent cut.

Thanks, rlw

 

[TresCrows]

The height control knob has detents which catch the lift control arms so to speak. Your problem is an improperly adjusted deck. Your deck should glide along with the rollers about one half inch above the grass blades. Get your BX on level concrete and adjust to get at least 0.5 clearence and then move out out on to a typical piece of your lawn and readjust to get the 0.5 if needed. The mower deck is being lifted off the detents when the wheels ride the ground all the time and it is not locking as a result--have you noticed that you cannot turn the knob when the weight is on the deck lift arms and you can when the improperly adjusted scalp rollers are carrying the weight. J