Stump grinder losing power

agjones · Jul 1, 2019

Hi all

My stump grinder lives a pretty harsh life. Yesterday's heat may have lead to a problem.

Losing power, rpms are about right but the tool stalls even when engaging in light work.

Is there a rebuild process for the internals?
Thanks for any help.

ponytug · Jul 2, 2019

Sorry to hear it.
Can I ask a question; Have you double checked that it isn't something wrong with your relief valve?

Similar RPMs, but stalling under light work sounds more like a relief valve than a motor. Usually a motor will lose RPMs as well as stalling easily.

One that had loosened would show the same symptoms, and ditto for one that had a bit of debris caught under the relief seal. Absent JJ's handy dandy pressure gauge on your PTO, I would be inclined to chat with Terry about how best to disassemble and assemble the relief valve to check for a blown seal or debris.

All the best,

Peter

agjones · Jul 2, 2019

Thanks, Peter. I'll be able to get a gague on it this weekend. Other attachments are functioning well which key me suspicious of the grinder.

I'll check with Terry next week.
Happy 4th!

1010 · Jul 2, 2019

Is the head belt driven? Could be slipping at the pump/motor connection...

agjones · Jul 2, 2019

Thx, direct drive.

m5040 · Jul 3, 2019

Direct drive - is it a splined coupler or? Can any slippage take place between the motor and cutter? Sheared key? Is any fluid noise coming from the motor that may change under load? Does the motor get hot quick?

agjones · Jul 3, 2019

Not hearing any unusual noise. Impossible to tell what's hot fast... It's 95 degrees... But I switched to the trencher and had the expected power, same with the power rake...

No slippage. Just really anemic.

Any body know the internals of the roller stator hydraulic motor? Could a seal have been pushed out?

ponytug · Jul 4, 2019

The fact other implements work does focus it on the grinder. Yes, I agree, it is probably a blown seal. Yes, it can be rebuilt, but I don’t know if PT sells a kit. You are going to need the seal kit and a really clean area to do it in. Tolerances are pretty tight.

Stump grinding has to be hard on the motors. When you do get it rebuilt or a new motor break it in slowly to keep the peak pressures low until all the seals have a chance to seat properly.

All the best,

Peter