BCS 853 dying when powering Berta Flail Mower

   / BCS 853 dying when powering Berta Flail Mower #1  

youngth

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Dec 15, 2021
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Tractor
BCS 853
I work for a farm that uses a BCS 853. I was using the Berta Flail Mower this week and the tractor was repeatedly dying within a few minutes of engaging the PTO and beginning to mow, regardless of the thickness of brush/grass, etc. that was being mowed. The tractor would run just fine with the PTO disengaged. I would engage the PTO at mid-throttle and then quickly throttle up to full. After engaging the PTO, the BCS would typically operate smoothly for a minute or two and then begin to oscillate where the power rapidly cycled up and down. The engine would die shortly after this and I'd have to restart it. I tried engaging the clutch to take it out of gear and reduce the load on the engine once the oscillations began but this wouldn't help; it would still die. Sometimes the BCS would run smoothly for a very long time and not die, so this effect was inconsistent.

When restarting the engine, the cylinders would be under so much compression that I couldn't pull the starter cord without basically having the starter handle ripped forcibly out of my hand. I would have to do the first pull very slowly to release the pressure. After this it was somewhat more difficult to start than in the past, requiring some futzing with the throttle and choke.

The farm owner who uses this machine far more than I do suspects there may be a fuel leak somewhere (although I don't know whether he's seen evidence of this on the undercarriage, ground, etc.) causing the engine to lose fuel pressure when under any kind of load from the PTO. I'm wondering if anybody has any other ideas of what might be happening?
 
   / BCS 853 dying when powering Berta Flail Mower #2  
I work for a farm that uses a BCS 853. I was using the Berta Flail Mower this week and the tractor was repeatedly dying within a few minutes of engaging the PTO and beginning to mow, regardless of the thickness of brush/grass, etc. that was being mowed. The tractor would run just fine with the PTO disengaged. I would engage the PTO at mid-throttle and then quickly throttle up to full. After engaging the PTO, the BCS would typically operate smoothly for a minute or two and then begin to oscillate where the power rapidly cycled up and down. The engine would die shortly after this and I'd have to restart it. I tried engaging the clutch to take it out of gear and reduce the load on the engine once the oscillations began but this wouldn't help; it would still die. Sometimes the BCS would run smoothly for a very long time and not die, so this effect was inconsistent.

When restarting the engine, the cylinders would be under so much compression that I couldn't pull the starter cord without basically having the starter handle ripped forcibly out of my hand. I would have to do the first pull very slowly to release the pressure. After this it was somewhat more difficult to start than in the past, requiring some futzing with the throttle and choke.

The farm owner who uses this machine far more than I do suspects there may be a fuel leak somewhere (although I don't know whether he's seen evidence of this on the undercarriage, ground, etc.) causing the engine to lose fuel pressure when under any kind of load from the PTO. I'm wondering if anybody has any other ideas of what might be happening?
Had to look that up, didn't know there was anything you could pull start that would run a flail.

I would change fuel filter, dump fuel in the tank, and drain the float bowl. Refill and give it a go. Oh, get the air filter as well. The weird thing with the pull you noticed, might be a little hot from running lean.

Best,

ed
 
   / BCS 853 dying when powering Berta Flail Mower #3  
What kind of engine? I have a wood chipper with a Kohler engine. Suddenly became hard to start. Remove spark plug, abd it turns fine. Something has happened to the automatic decompressor mechanism. Maybe the same problem with yours.
Haven't had time to take mine apart and see inside tho.
 
   / BCS 853 dying when powering Berta Flail Mower #4  
Hi youngth ;)

Chances are that the BCS 853 that you have been working with, has a Honda GX 390 gasoline engine, which is the same engine that I have on my BCS 740.

I only experience the oscillating engine speed shortly before the fuel tank is getting empty, and the engine simply runs out of fuel. This is what one would expect, and what makes me think that you might have a fuel issue. The fact that you have this experience so inconsistently though, puzzles me. If the engine is starved of fuel for some reason, it should happen all the time, and not allow the engine to run for a longer period of time sometimes 🤔

When it comes to your second problem, I am sure that Andrew is right about the problem being the automatic mechanical decompression system, as I have had the same problem. This system opens the exhaust valve slightly on the compression stroke during start, thereby reducing compression and the force needed to turn the engine, and it also prevents the kick-backs that you have experienced. If you check the valve clearance, I would be surprised if the exhaust valve does not have a much too wide gap. A too wide clearance gap on the exhaust valve prevents the decompression system from opening the valve, as its action is set off by the extra slack.


Best regards

Jens
 
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