Bush hog blade stopping

[yanmars]

I was mowing grass with a 5 foot light duty King Kutter brush hog using a 40 horsepower NH tractor. It cut well in areas I had cut earlier this Spring but when it got into 2 foot tall grass (not that thick) it caused the blade to nearly stop but enough it did not cut at all. The mower has always been greased, the shear bolt was not damaged or broken. The blades are dull. When I would get back to the prior cut grass the blades would pick up speed and cut again but it had nothing for the taller grass. The tractor was moving at slow speed with engine RPM near 2500.
The problem is most of the grass is tall as my main tractor and mower have been down for 3 months waiting for an odd sized O ring. Really need to mow the tall stuff with what I have. Any thoughts or suggestions?

 

[airbiscuit]

Not sure this will help, but if you adjust the rear tail wheel so the rear of the mower is elevated, the mowed grass can more easily exit the mower. It can make a difference in the power needed to spin the blades.

 

[Williy]

Can you raise the brushhog then cut and then lower it
and keep making passes till you get it cut
and blades not sharp don't help it just makes it harder
to cut and takes a lot more power to bull threw

willy

 

[Roadworthy]

The mower blades slow down. Got it. Does the tractor engine slow down as well? If the mower slows and the tractor engine does no slow you may have a slipping clutch.

 

[yanmars]

It is a hydrostatic transmission. The engine does not bog down, just the bush hog.

 

[WranglerX]

Is there a clutch on the mower PTO shaft? ....Something similar to image below...

 

[pjbci]

If blades are slowing down but not the engine. Something is slipping. The clutch pictured above or the clutch inside tractor.

Rare but possible with some rotary mowers, the output shaft on the gearbox has sheared the key but continues to spin from friction of a tapered shaft and tight bolt.

 

[yanmars]

No slip clutch on the mower and the shear bolt is not broken. Hydrostatic drive on the tractor.

 

[Tx Jim]

Sounds typical for pto clutch slipping. Hyd engaged pto clutches normally have a test port to check hyd pressure. I suggest to check pto clutch pressure.

 

[Roadworthy]

I don't know how your tractor's built but my Kubota is HST AND has a clutch. When the clutch is depressed it disengages the PTO and my mower slows down. I suspect if that clutch was slipping the mower could slow down in use. Even with HST you can have a defective clutch.