sudden and violent PTO engagement with new Kubota MX5800

[rbtjr]

We have a Kubota MX5800 with about 14 hours on it. The MX PTO is engaged electrically by pressing a switch that locks in place until you press it again to disengage the PTO. I have engaged the PTO five or six times so far using our brush hog. Each time the PTO engagement has been very abrupt and pretty violent. The PTO engagement is much more violent that I have experienced with prior tractors for which the engagement was via a clutch you could engage very gradually and smoothly. The PTO engagement on our new MX makes the rotary mower shake badly and violently. The mower is new from Everything Attachments and I have no reason to believe that the mower is the problem. Do any of you owners of Kubota MX tractors that have the electric PTO engagement system have a similar problem? If so, what is the fix? If not, I would like to know that your PTO engagement works well so I will have some data to tell my dealer about when I ask for the fix. Thanks in advance for your feedback.

 

[k0ua]

What RPM are you engaging the PTO?.. You should always engage the PTO just above idle with the cutter raised a bit to make sure there is nothing under it for the blade to hit. See if this helps. But electrically actuated PTO's do engage more violently than what a human can do with slowly letting out the clutch. But if you have the RPM's up it is really violent.

 

[ovrszd]

I'm afraid that's the nature of the beast. Do your engagements at engine idle to minimize the shock to the cutter or any other PTO attachment.

 

[Coyote machine]

Got to go with lowest engine RPMs for PTO engagement possible to minimize torque shock to your mower AND your tractor's drivetrain.
You could also ask Travis at EA; he knows Kubotas and his hogs/mowers too. He might be familiar with the issue you describe with the Kubota model you have....
Can't hurt to ask..
The only other thing that comes to mind for me is the faint possibility that your PTO shaft is out of balance and causing some issues because of it's knuckle joints being out of sync - but it's remote at best....
Once it gets going to speed, does the shuddering stop?

 

[rbtjr]

Yes, I always engage the PTO at the lowest possible RPMs, and with the implement raised.

Good point about asking Travis. I will do so.

Yes, the shuddering stops when the PTO gets up to speed. But today the engagement was so violent once that the tractor shut off and wouldn't start even with the PTO switch turned off. I disconnected the PTO shaft to the mower and then the tractor started.

Thanks for the feedback.

 

[RandyT]

I know what you are talking about. My DK45S is abrupt also. Engage rotary cutter at idle and cringe, with the slamming and shaking until it gets up to speed. My tractor idles at about 1000, and at 1500 I can shear a 1/2 grade 2 bolt used as a shear bolt.

 

[arizona98tj]

I have a Massey Ferguson with a similar electric PTO clutch. Starting my brush mower....it is almost scary given how bad it sounds. In contrast, starting my PTO wood chipper is about as smooth as can be. Go figure.

 

[David_Kb7uns]

Only other ideas is, what regulates the pressure or flow in the PTO circuit and is there a way to put a flow restrictor in to slow down engagement.

Will it get better after things break in and does the type or weight of hydraulic fluid have anything to do with how it engages?

David

 

[rbtjr]

Only other ideas is, what regulates the pressure or flow in the PTO circuit and is there a way to put a flow restrictor in to slow down engagement.

Will it get better after things break in and does the type or weight of hydraulic fluid have anything to do with how it engages?

David

Good questions. I don't know if there is an adjustment but I'll find out. The hydraulic fluid is what came in the tractor. I had a leak which was fixed by the dealer, and the hydraulic fluid was topped off with the recommended fluid. I'm going to investigate some on my own, ask the dealer what can be done, etc. I'll report back about what I learn.

 

[nybirdman]

Check to see if the BH blades are "straight" before engaging.

 

[TSO]

Sell it and get Massey 16xx or 17xx premium series, which comes with a "PTO soft start" feature.

I'm kidding of course (about selling yours... But not about that feature).

As already stated, that is what you get with electronic PTO engagement and no clutch. The reason it happens on rotary mowers is because the blades are "flung" out, and straighten, with inertia. Once they are extended, they regain balance. Each blade (two) is bolted to a center hub, directly across from eachother. But they are able to pivot on that bolt, which allows for the blade to "give" a little if it meets an object it can't cut thru. What usually happens when you shut down the mower, is that the blades naturally rotate on that pivot bolt and fall out of balance until you restore inertia again by turning it back on.

 

[boggen]

Only other ideas is, what regulates the pressure or flow in the PTO circuit and is there a way to put a flow restrictor in to slow down engagement.

Will it get better after things break in and does the type or weight of hydraulic fluid have anything to do with how it engages?

David

adding to...

goto kubato website
goto parts
goto part lists
search for your MX5800
expand "clutch/transmission"
click on C41400 PTO CLUTCH VALVE (COMPANENT)
#130 = part# YW479-10430 = orfice plate (0.8)

smaller size hole, might help, smaller hole would be like slowlying shutting off a kitchen sink from a large amount of water to a trickle of water. the hole size = a valve set at a constant partially opened up. not fully open, and not fully closed but some place in the middle.

==========
also the spring/ball = check valve. might have something there. not enough spring pressure or to much spring pressure. not sure how fluid flows through it all. so this might not have any effect what so ever. i would need to see full hydrualic diagram. and parts. to see if check valve is protection. or if it is there to keep PTO from reversing. or other.
#30 part# TA040-69330
#20 part# 07715-01605

===========
check all your fluids before starting it up in the morning. just because they said they did, or you assume they did, does not mean fluid was added to correct levels.

many times some of these are combined into one, some times they are seprated. i do not have a clue about your tractor.
--engine oil
--hydraulic oil (generally some place up in front around engine, used for FEL, and hydraulic ports on rear of tractor)
--power steering oil (some times same as hydraulic oil above, some times separate and you check at the steering pump located around the engine)
--transmission oil (between your feet or some place on side of transmission generally)
--rear end / pto. can be same as transmission oil. some times another spot to check fluids possibly on rear of tractor.

 

[kneedeep]

As already stated, that is what you get with electronic PTO engagement and no clutch. The reason it happens on rotary mowers is because the blades are "flung" out, and straighten, with inertia. Once they are extended, they regain balance. Each blade (two) is bolted to a center hub, directly across from eachother. But they are able to pivot on that bolt, which allows for the blade to "give" a little if it meets an object it can't cut thru. What usually happens when you shut down the mower, is that the blades naturally rotate on that pivot bolt and fall out of balance until you restore inertia again by turning it back on.

This is what is happening when the PTO is engaged, both my tractors do it and the 5500 has a manual engage lever.
The drive shaft should be as straight as possible also to reduce stress on u joints when engaging.

 

[Coyote machine]

Yeah, how much are you raising the mower before engaging the PTo switch? Too much angle may be making your drive shaft have a hard time turning at startup, (high torque start when switch is engaged), and that maybe transferring it's out of balance to the mower gearbox. Least amount of angle for the U-joints at start-up would be best.
Have you checked the mower's gearbox fluid? If low or you hit something hard it could be leaking, or might have run dry, from underneath the gearbox/mower, and that could really mess things up. And you may have smacked a rock or stump or some other immovable object and bent one of the blades, which would show up more as imbalance when torquing up, vs. when running at speed?

 

[TripleR]

As ovrszd said, nature of the beast, it is no different with other similarly equipped brands. I grew up on the old, simpler tractors and equipment, so the shaking on today's modern tractors is no big deal.

 

[RPW]

Here's something simple. Add a slip clutch in line with the mower. That should absorb alot of the shock and help to keep from damaging the mower or drive train.

 

[TSO]

Here's something simple. Add a slip clutch in line with the mower. That should absorb alot of the shock and help to keep from damaging the mower or drive train.

I would hope not... If a slip clutch would slip just on startup, it would mean it was waaaaaay to loose.

 

[ovrszd]

Yes, I always engage the PTO at the lowest possible RPMs, and with the implement raised.

Good point about asking Travis. I will do so.

Yes, the shuddering stops when the PTO gets up to speed. But today the engagement was so violent once that the tractor shut off and wouldn't start even with the PTO switch turned off. I disconnected the PTO shaft to the mower and then the tractor started.

Thanks for the feedback.

Not to sound condescending, your tractor doesn't "know" if the PTO shaft of the cutter is attached.

 

[ovrszd]

I would hope not... If a slip clutch would slip just on startup, it would mean it was waaaaaay to loose.

True that.

 

[TSO]

It probably only stalled because there was too much load on the engine at that moment ... (While the blades were sorting themselves out)