Lawn Mowers Electric PTO handy Hints

Published on February 20th, 2015 | by Jacks


Electric PTO Clutches Handy Hints

The two most important requirements for a successful clutch application or installation:

  1. Anti-rotation device must allow both axial and radial free-play. Failure to allow this free-play will result in field bearing failure. The greater the restriction the faster the bearing will fail.
  2. Mounting bolt torque to be minimum of:
    3/8"-24 UNF use Grade 8 bolt torqued to 40/45 lb.-ft. (Grade 5 bolt is unacceptable)
    7/16"-20 UNF Grade 5 or 8 bolt torqued to 50-55 lb.-ft. (Grade 5 or 8 bolt is acceptable)
    M 10 X 1.50 Class 10.9 torqued to 55-60 N-m.

Install mounting bolt and retaining washer and torque to spec for the clutch to work properly.

Use Grade 5 or Grade 8 bolt only. Minimum torque:

  • 7/16 in. UNF bolt is 50ftlb/67 Nm
  • 3/8 in. UNF bolt is 31ftlb/42 Nm
  • M10x1.5 bolt is 35ftlb/48 Nm

Most applications that mount directly to the crankshaft use a “CCW” for standard mount (pulley away for engine).
A “CCW” rotation is normally used for reverse mounting (pulley towards engine).
If a clutch is mounted incorrectly then the springs will be run in compression and it will cause the springs to fail.

Warning – Anything less than required mounting torque could result in clutch failure, thus voiding warranty.

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About the Author

Jack's Small Engines has been providing parts for outdoor power equipment online since 1997. We also run a service center for outdoor power equipment like riding mowers, snow blowers, generators, chainsaws, and just about anything else.

15 Responses to Electric PTO Clutches Handy Hints

  1. don says:

    I have a troy bilt riding lawnmower model 14ay809p063 50″ cut 23hp kohler engine
    I can mow all day in granny low but as soon as i put it in high the pto cuts off I replaced the pto switch and the relay . but to no avail. You can start off in high and blades rotate but ony last for a minute or 2 never cuts off while its in low gear. what do you suggest?
    Thanks for your help

    • Jason says:

      I have the same mower & just replaced the PTO. My bolt is 5/8″. I torqued to 55lbs. Now my clutch is getting hot, smoldering & shuts down after it gets hot. Do you know the proper torque specs for this bolt? I have a feeling it’s lower, like around 40, as when I removed it by hand, it was little effort & when when using the torque to reinstall, 55 seemed way cranked tighter than when removed.

      • Gary P. says:

        Don’t think torque has anything to do with your issue. If the 5/8″ mounting bolt has the proper thickness washer (probably 1/4″), the proper torque is to just make sure the clutch is seated as designed and won’t back off.

  2. Dale Schultz says:

    Does a kawasaki 23 horse power liquid colled moter have a safety shut down if the water pump blows
    I think my pump blew and now the mower will run but not the blades
    You can drive the mower but as soon as I engage the PTO it dies out
    Shut down the PTO it runs just fine I have taken each spark plug wire off one at a time and the machine will run

  3. Lance says:

    I have a zero turn rz4619 huskqvarna and when I engage blades u hear it engage but when I start it and engage it dies. I.
    Am getting the volts needed down there so how do you know when it is just time to replace the clutch??

  4. Corey says:

    Most applications that mount directly to the crankshaft use a “CCW” for standard mount (pulley away for engine).
    A “CCW” rotation is normally used for reverse mounting (pulley towards engine).
    If a clutch is mounted incorrectly then the springs will be run in compression and it will cause the springs to fail.

    I’m a little confused on this, when then is a CW rotation used? I’m not sure I understand what you mean by away from engine and towards engine. What if the clutch is used to drive a shaft with the clutch mounted to the driven shaft? Is a CW rotation needed for that application?


    • Corey says:

      This states a CCW is used for pulley towards engine, pulley away from engine. I think one of the two was supposed to be CW correct? Is CW supposed to be used for “pulley away from engine” meaning the clutch pulley is mounted on a shaft other than (away from) the engine???

      • matt says:

        I would love to know the awnser to this I am trying to source a pto clutch to fit on the stub shaft on the front of a engine. Is the rotation stated as your looking at the pully or looking at the stationary section?

        • Dean Ricke says:

          I am confused as well need verification i have a cub zero turn engine is cw at flywheel and pulley is below pto need to know rotation of pto clutch

  5. Electric John says:

    I just ordered from Jack’s, and replaced the 2 drive belts on my Snapper Pro Snapper Pro Mod# NZM27613KH
    *Belts: Hydro Pumps, Drive Belts: OEM Replacement Belts 265-392 Stens, and after install I checked by running briefly, engaged the PTO, and disengaged, turned engine off. All was operational. Great. Then I proceeded to mow. When finished, I pushed the PTO button down/off and the blades didn’t disengage, had to kill engine to stop blades. Looked underneath, and one of the two belts broke. That alone wouldn’t cause the blades to not disengage since the machine operated for years with only one of the two belts… so what is causing the malfunction? Is it the electric clutch, does it just need adjusting? The clutch wires looked to be a lil raw from belt breaking so I wrapped em up in electrical tape. Do I need to test the clutch with a meter? How exactly? Any advice will be appreciated. Thank you.

  6. Randy says:

    Hi, My Hustler Sport 48″ ran fine since 2009 but twice this year I have had trouble with the bolt in the end of the crank: first time the bolt fell out and it dropped the clutch. Replaced bolt with a Grade 8 and this time the bolt broke. Advice?

  7. Dawson says:

    Quick question. I have a 23 hp Kohler engine on a 52″ deck scag zero turn mower. The engine was freshly rebuilt and we were going to reinstall it ourselves. Now we hooked everything up and rewired things. When you turn the key the blades turn as well (the blade switch is in the off position at this point) therefore not supplying enough juice to turn the engine over as it struggles. Why would the clutch not be disengaging? When the blades are turned on, naturally the mower won’t even turn over. Yet in the off position it will turn over and continue to spin the blades. Clutch issue? New clutch? Wiring issue? Any help would be greatly appreciated

  8. justin says:

    what does the first tip mean?

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