Buying Used Rotary Mower

[RidgeHiker]

It is an SQ600. The manual lists the gearbox as 55 hp as you said Zebrafive. At the same time it states for "recommended tractor hp 25 - 40. Don't really know why the difference. Perhaps the PTO shaft or other parts are not rated as high??? Glad you pointed the 55 hp gearbox out, I feel better about that.

 

[RidgeHiker]

That was a fair price to start with. You got a good deal. Shear pins on a high HP tractor can be problematic. Make sure you keep throttle low when you engage the PTO.

I have been experimenting with that. If the rpms are up at all it really clunks in when engaged. Even with the rpms at the minimum, probably 1000+ (would need to look) it still clunks in but not as hard. Helps if I turn the knob slowly to engage but still not smooth. Is this normal???

 

[ovrszd]

I have been experimenting with that. If the rpms are up at all it really clunks in when engaged. Even with the rpms at the minimum, probably 1000+ (would need to look) it still clunks in but not as hard. Helps if I turn the knob slowly to engage but still not smooth. Is this normal???

Not familiar with your tractor model. If turning a knob engages PTO it's probably doing it electronically and nothing you do can soften the shock load beyond doing it at idle rpm.

 

[Hay Dude]

Some tractors have a soft start PTO.
Gearboxes HP: Although a gearbox could be rated for 55HP, if there’s a weaker “link in the chain”, that can knock down the maximum input HP.
I would probably want my gearbox to be rated higher than my PTO shaft. That way if there’s a failure, the shaft is probably a cheaper repair than gearbox.

Start/stop: I am running a 135HP tractor into a rotary cutter with 200+HP gearboxes. I always start at low rpm, then increase throttle to reduce shock load on my PTO, PTO shafts and gearboxes.

Also, throttle down your tractor before you shut off the PTO (unless it’s an emergency shut down) to reduce excessive wear.

Blades: the blades should be straight (no chunks missing) but not overly sharp. You want your lawn mower blades really sharp, but that’s because you want the tips of the grass blades healthy. “Ragged” grass tips are more subject to disease. Bush hog tips are fine if they leave a somewhat ragged cut, because it helps kill the brush.

 

[RidgeHiker]

Checked from underneath. There is a little play when turning the blades. That might be the cause of the clunking.

 

[JethroB]

Hay Dude, where would the extra wear be when shutting down PTO at high RPM’s?
thx

 

[Hay Dude]

Jethro B,
PTO clutch brakes wear out faster when you shut off a bush hog at a high speed than if you throttle down against the engine to a lower speed, then shut off the PTO.

”Kubota Tractor PTO Problems Tip: This problem occurs when a bush hog, for instance, is shut off when the power is cut from the PTO. The blades continue to turn because of their weight. It should be noted that when the PTO is off, its clutch is disengaged. However, its brake is still engaged. The brake plate tab and PTO clutch holder suffer wear. *The implement should be turned off at idle speed only.*”

full article: Kubota Tractor PTO Problems - How to Engage PTO | Bobby Ford Kubota

 

[DieselBound]

$500 is a good price. I paid $800 for a very beat up BH26: six footers are harder to locate in my area.

Try the blades as-is to see how they do: it can be instructive. For live brush it's better to have semi-dull blades as that fractures the brush and causes more stress: the aim is to kill the brush.

As noted, engage your PTO at low tractor RPM (I always look to raise the mower a bit before starting). You may feel a bit of wobble until things balance out: blades can start out folded up.

I'd recommend checking that the stump jumper assembly is tight on the shaft: raise the mower and with everything off and nothing moving, rock the stump jumper up and down- if it can move up and down then it may be tightened. I had the stump jumper assembly on my BH26 come off: interesting to say the least: might not have happened if I'd have checked for play and tightened (though I had to double up on the washers in order to get it tight enough on the shaft- tapered shaft and things wear a bit- best to catch before the splines get chewed up!).

 

[TheMan419]

I have been experimenting with that. If the rpms are up at all it really clunks in when engaged. Even with the rpms at the minimum, probably 1000+ (would need to look) it still clunks in but not as hard. Helps if I turn the knob slowly to engage but still not smooth. Is this normal???

Yes. Getting those big blades spinning takes a lot of work. Doing that when the egine RPM's are at 540 PTO rating makes the blades want to go from zero to 100 like that. Lower engine RPM they are going from zero to 40. Then ramp up the engine RPM.

 

[Aquabird]

Since you guys are all talking about his new(to him) mower deck, I have a question.
Do newer mower decks spin the blades faster than the older ones?

Yeah, I know the RPM of the tractor spins the PTO at that speed, but the newer ones might have gearing inside that turns the blades even faster??

The newer Zero turn mowers has a faster blade speed than older ones, and the same is true for push mowers.