PTO clutch

What would cause a new clutch to burn up? About 5 hours and looks like a bearing seized and ruined the clutch on a 24hp. Z mower. Had torqued it to 55lbs per instuctions, belt pulleys aligned, and mowing normal height grass. (not stressing the machine at all) gregjo1948:confused2:

If the bearing seized after only 5 hours of operation, I would suspect a bad clutch. Only other thing I can think of could be a problem with the electrical system,causing the pull-in coil to over heat.

What could cause the coil to over heat? Is there a constant 12 volts going to the clutch or does it somehow drop after once it has been engaged? Thanks, gregjo1948

With a properly functioning charging/electrical system, the clutch will get 13 plus volts DC.
Did you burnish the clutch correctly? If not, the clutch will slip which creates unwanted heat that could cause the bearing grease to either burn or run out past the seal. I did receive a new clutch with one bearing that had no grease in it. Since then I always inspect the bearings on new clutches by carefully lifting up the edge of a seal to look in. I have had clutches last 1,000 hours down to 100 hours.
Check the wiring diagram for your specific machine to see if there is a diode installed in the clutch wiring and if so, isolate it and check it with a ohmmeter.
Mad Mackie in CT

Mad Mackie, please educated me on electric PTO clutches used on today's lawn tractors. Where is the bearing seal? Where are you putting grease? To my knowledge the top half of the clutch contains a electromagnetic coil and has a self contain key which fits into the keyway on the crankshaft. When the PTO switch is engaged, the coil draws the clutch cup (which is also part of the clutch pulley) up against the magnet making it one solid unit. Most clutches also have return springs to push the two halves apart when the power is turned off. There is also a clutch stop which keeps the top half housing from turning. No posse that I have ever seen calls for grease or has a grease seal. Is there a new type of clutch that I have never seen or heard about.

Hi Rivets,
I hope that you are "pulling my leg" about electric PTO clutches, but here goes!!
Having been an aircraft mech over the years I have a set of tools for safely removing O rings and I use some of these tools to lube bearings that have non metal seals installed on them.
Every electric PTO clutch that I have dealt with has at least two bearing and clutches with more than one pulley may have more than two bearings.
I use a new scribe that I have gently removed the sharp tip from using a sharpening stone. This I use to initially get under the bearing seal. I follow it up with another tool which is a brass rod that has been hammered flat and I use this to gently lift the seal so I can slip in a hypodermic needle that has a grease fitting installed onto it. This is an automotive tool that is used to do a fast and dirty lube to a CV joint on a front drive vehicle by sticking it thru the boot and pumping in some grease. The grease that I use is sold by some bearing manufacturers, but there are aftermarket suppliers that package similar grease.
All electrical PTO clutches for power equipment have a brake incorporated into them and many are directionally sensitive. New clutches need to be burnished when installed, otherwise they will slip which causes excessive heat that can adversely affect the bearings and the V belt. Most have an adjustable airgap so the brake will properly clear when the clutch is engaged and not drag which also can also cause unwanted excessive heat.
Go online for both Warner and Ogura and there is technical info for PTO and other types of electrical clutches, however nothing about lubing the bearings.
The pulley bearing turns when the PTO is not engaged, the coil plate bearing turns all the time the engine is running and at the same RPM as the engine. This is the bearing which has the sleeve with the key slot that engages the key slot in the crankshaft.
Mad Mackie in CT :laughing::biggrin::smile:
Was Boomer able to help you finding an Onan flywheel???

I don't understand what the advantage is with the electric clutch over a manual clutch ( pto set up with a lever )

At $250 a pop I don't think I want a mower with one.

(( racing is the only sport that you need two balls ))

First off the Feds safety folk got involved in the 80s and mandated that a brake be incorporated into the mower clutch system. Secondly, the design of ZTR machines doesn't lend to having a manually engaged deck clutch.
I know what it is like at $250 or more at a pop, one of my machines is on it's 5th clutch, but the machine has almost 2,500 hours on it and an operator, me, that pushes machines hard year round!!!
Mad Mackie in CT:laughing::biggrin::smile:

Rivets-- I believe Mad Mackie is talking about the seal on a sealed bearing, not a seperate seal. Mad Mackie-- I did not burnish the clutch. I wasn't awear of the need to do so. Wouldn't you think they would supply that info with installation instructions. There were no instuctions on the torque specs either, but I found that online. Thanks for the education!:smile: gregjo1948

No, I was not pulling your leg. In my 40+ years of teaching and working on small engines and the equipment they run, I have never greased a clutch bearing, nor heard of it being done. That being said, I don't work on the larger clutches. Have been going to up-date schools and was certified for warranty work by many of the equipment manufacturers and that was never brought up. Don't remember the last time I had to burnish one before installing, although I have had to send a few back that were so far turned over that they would not go on. With seals, I would understand if you were talking about the bearing seal and not a grease seal. I have see clutches that have failed due to being seizure, but 90% are due to coil failure, 5% due to bearing seizure and 5% due to stupid operators. The bearing seizures that I can remember happen either in the first 25 hours or after many years of use. From your description, I don't think I am going to change my procedure when working on them, but it will be in the back of my mind, what's left of it.