Helpful info regarding clutch use

   / Helpful info regarding clutch use #1  


Platinum Member
Mar 4, 2008
Southwestern Wisconsin
BCS 850 diesel and 735 diesel
Hey all,

The flail mower is a great attachment. It cuts anything up to 3/4 inch brush and mulches it very fine. Unfortunately, I've seen a couple machines come in with smoked clutches now. Joel wrote up a nice little info sheet on proper clutch use. I'll copy and paste it here.
From Earth Tools' site -

Earth Tools

Proper Clutch Engagement & Use on Walk-Behind Tractors
(For Standard Type Clutches)

Before shifting your walk-behind tractor into a wheel-speed, engaging the PTO (implement drive), or shifting between forward and reverse, the clutch handle (on bottom of left-hand handlebar grip) must first be squeezed all the way, to disengage engine power from the machine during shifting (the same way you would on any standard-transmission tractor, car, motorcycle, or truck when shifting gears).

Sometimes, when shifting gears OR trying to engage the PTO, you may find that the shift lever does not want to engage fully. This is because the gears in the transmission are not aligned properly. To get the gearshift or PTO lever to engage fully, put firm pressure (NOT shoving or jerking...just firm pressure) on whichever lever you are having difficulty with, and release the clutch lever very slowly, and as soon as the gears begin to rotate, the pressure you have on the gears will pop the gear into place as soon as it aligns. (The technical term for this type of operation is feathering the clutch).

Once your shift levers are fully engaged, when then letting out the clutch lever to engage power to your tractor & implement, you should never exceed about 1 to 1.5 seconds to fully release the handle. On lighter loads, such as tillers, sickle bars, power harrows, rotary plows, etc.: the clutch handle can be released virtually instantly (1/2 second or less, basically just dropping the handle), but when operating heavier loads (implements) that operate at a high RPM (Revolutions Per Minute), more care must be taken to not overload the engine OR damage the clutch. As a rule, you are better off bogging the engine down by letting out the clutch quicker, rather than letting it out too slowly and wearing the clutch lining prematurely through excessive heat/friction.

Here are some tips when engaging heavy-load implements which need to operate at FULL engine throttle (such as flail mowers, larger brush & finish [lawn] mowers, Chipper/shredders, etc.):

---Have the engine at 1/3 to 1/2 throttle (rather than full throttle) during let-out of the clutch, then, after the clutch handle is fully released, accelerate the engine to maximum throttle.

---During initial start-up of the implement (that is, whenever the implement is at a dead stop), DO NOT have the implement "under load" (that is, a rotary mower should not be starting up while in high grass...the mower needs to come up to speed, and THEN encounter the high grass/weeds/etc.) If you are starting the mower up from a dead stop in the middle of a field of tall material and there is no unmowed place to get started in, you can always push down on the handlebars to lift the mower off the ground during the first few seconds of the mower getting up to speed.

---You can even do a "double-clutch"...that is, let the clutch out pretty quickly, and let the engine pull waaaay down for a second (nearly stalling it), while it starts getting the implement up to speed, then squeeze the clutch handle in for a second or two and let the engine "recover"...the implement is still spinning, so when you release the clutch a second time, the engine hardly bogs at all. It's the INITIAL start (from a dead stop) on high-RPM implements that is the hardest on the clutch. (This trick works best for implements with HEAVY rotating flywheels that have to come up to speed...BIO-90, 100 & 150 chippers, 32 brush mowers)
When mowing, and maneuvering the tractor between forward and reverse (or when shifting between wheel speeds) the same care does not have to be taken as above, as long as the mower blades are still rotating somewhat. If they are, you can pretty much drop the clutch handle instantly in between shifting, and leave the engine at full throttle. Excessive slipping of the clutch (taking too much time to release the handle, OR squeezing the clutch handle partially when the engine is bogging down, OR trying to use the clutch as a speed control by squeezing the clutch handle partially to slow the machine down) when the machine is under load WILL result in clutch overheating, which causes premature clutch wear and possible complete clutch failure if the clutch is severely overheated. ***This is no different than what will happen if slipping the clutch excessively in a car or truck. *** (PLEASE NOTE: feathering the clutch to engage gears [as described on the first page] is not a problem, since the machine is not under load at the time.)

As the clutch lining is worn away during use, the clutch linkage/cable actually "tightens up", meaning that you may notice that you actually have to reach further down now the grasp the clutch handle...what "free play" was in the linkage/cable has been used up by the lining wearing away. If the wear to the clutch lining EXCEEDS the amount of free play available in the clutch cable & linkage, the cable/linkage becomes TIGHT, and the clutch will begin to slip under load, therefore not transferring power to the tractor and implement. Attempting to operate the machine in this condition will further damage the clutch, for the same reason: it is slipping, so it will quickly overheat.

To get a clutch that will hold (transfer power) again, all you may have to do is loosen up the clutch cable, to get more slack. If the slipping is experienced in the front-PTO (mowing) mode, you may notice that the clutch does NOT slip when the tractor is in the rear-PTO (soil working) mode?...this is because when the handlebars are in the soil-working mode, there is more slack in the cables, because the cable sheathings are not being "bent" so much. Please see our video for adjusting a clutch.

If the clutch is severely overheated, the clutch lining will wear very quickly due to "crumbling" of the burnt lining. Usually, if this has occurred, there will be a very nasty burned clutch smell (like overheated brakes). The only fix for this is a new clutch (or clutch lining, if it is available separately).

The typical service life of a clutch in this equipment is anywhere from 1000 to 2000 hours of use. I have a BCS 850 tractor with 12hp engine on it; I got about 1800 service hours out of the original clutch lining... and I don't baby it; I use it hard. However, when "slipped" excessively and overheated, I have seen some folks ruin a brand-new clutch lining in less than half an hour. Hopefully, your reading, understanding, and implementing the above info will keep you OUT of the latter category!!

One final bit of advice regarding BCS tractors with standard clutches: PLEASE MAKE SURE TO LOCK THE CLUTCH LEVER ON THE HANDLEBARS IN THE SQUEEZED POSITION WHEN YOU ARE NOT USING THE TRACTOR!! This keeps the clutch lining & plate from sticking together during periods of storage, particularly in humid environments. After reading the above thoroughly, if you have further questions, please contact us.

Joel Dufour
Earth Tools Inc.

To add to what Joel says -

- With the Berta flail mower, remove the baffle whenever you can. It is only needed when you want to mulch material super fine. If you're just mowing a grassy area or paths through the woods, the baffle isn't really necessary and requires extra torque.

- Always run mowers (flail, rotary, drum) at full throttle. If you want to mow at a slower speed, shift down a gear. If you run at less than full thottle, you're not at the engine's peak torque and it will bog down quicker in hard going. You're also giving up RPMs on the blades, making them less effective at chewing through material.

- Keep your clutch properly adjusted. before you run your machine on any attachment, check the amount of movement the clutch cable has at the clutch. You should be able to move it side to side roughly 1/2 and inch. More, and the clutch won't disengage. Less, and the clutch won't fully engage.

I hope this info helps someone.
   / Helpful info regarding clutch use #2  
Too late.

Actually, I had read that before I burnt up the clutch, and I was doing most of it, aware it was a problem, but the previous owner (I assume - I hope it wasn't Earth Tools) had incorrectly adjusted the clutch too tight on the cable, making it so that when the clutch handle was fully released the clutch was only partially engaged. To top things off, someone cut the end of the cable off so there wasn't enough adjustment left to remedy the problem - although by the time I discovered the problem, it was too late.

So I swapped the cable from my 730 onto my Grillo, but as I said, it was too late, so now I have to replace the clutch.
   / Helpful info regarding clutch use #3  
The good news... on the 107D the clutch is easy to rebuild.