Trouble with rotary mower shear pins

[Oneday997]

Howdy Folks - I have an XR4140 and have been having constant problems with the shear bolts in my rotary mower breaking. The PTO engages pretty roughly no matter how you engage it (e.g. I throttle down to 1,200 RPM or so, slowly turn the switch) and after 2-3 engagements, the bolt simply breaks. I spoke to the shop that sold the tractor to us and they said try a grade 5 bolt as opposed to the grade 2 the mower specifies. Said grade 5 would be fine and wouldn't damage the tractor, but don't go above that. Just curious as to it anyone else has experienced the same thing and found a solution. I tried mowing last weekend and went through no less than 6 bolts before I finished up Many thanks!

 

[Rebeldad1]

upgrade the pto shaft to a slip clutch. no worries about breaking the pto

 

[radios1]

this sounds like you have a bad gearbox on the mower, have you tried turning it by hand to see if it feels like worn or binding gears?..

 

[Avenger]

I had the same problem. No matter how slow you engage the switch, its an electrical switch. Its either on or off. Its not like the old school lever actuated engagement that you can feather on. Best practice is to still start the PTO at lowest possible RPM.
The issue isn't with the gear box/pto shaft, your tractor, or the mower. Its a fault with all three. If the tractor had the before mentioned lever engagement, this wouldn't be an issue. If the gear box/pto shaft was better quality and had a slip clutch, this wouldn't be an issue. If the mower didn't have swing out blades that curl up when stopped and then violently swing out causing horrendous vibrations when turned on, this wouldn't be an issue.

The only thing we can do the alleviate the issue is to install and adjust a PTO slip clutch. Trust me on this, it is the best thing you can do. You will want one for every PTO implement you own if not already equipped. Here is the one I installed on my rotary mower: Add on Rotary Cutter Slip Clutch Easily Add a Slip Clutch to Your Shear Bolt Pto: Amazon.com: Industrial & Scientific

Make sure you check your gear box shaft to see if it is smooth or splined. Mine was smooth.

They are expensive, but totally worth every penny!

Here is a very recent video of how I adjust my slip clutches. YouTube

Hope this helps.

 

[Avenger]

Oh! And you can use a grade 5 bolt (I did, went through 11 of them before I got the slip clutch) though is not really recommended and you will still snap them on start up. Only you might get a few more on/offs before they break.

 

[Oneday997]

thanks for the info on the slip clutch. Sounds like this is probably the way to go. At first I thought the gear box might have been binding up, but the blades spin easily and freely by hand when not engaged. I can actually feel the bolt break on the engagement of the PTO. At the rate I'm going, I'll have spent more on bolts then on a slip clutch before long lol!

 

[RandyT]

At 1200 rpm I can snap the shear bolt also with my DK45S. Need to start the mower at full idle what ever that is. Around 1000 on my tractor, and even then is rough.

 

[Bluesteel]

Slip clutch is the only way to go. I had the same issues until I upgraded.

 

[oldnslo]

If and repeat if LS installed an orifice in the PTO line to limit clutch actuation time and it is accessible you could possibly play with different orifices to make engagement less abrupt down side of this is that it will take longer to engage when oil is cold and slip the clutch even more. Once fine tuned they work reasonably well.

agree that slip clutch on PTO is probably the easier alternative.

 

[fordtrucknut]

Not sure if yours has it, but my 3037 has a switch on the dash to beable to engage the pto with the clutch, that's the only way I can engage my brush hog without blowing bolts.
Once it's running I just flip the switch back the other way and the pto stays on for driving.