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Strong Brush Cutters Modifications & more

Evansaw

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Hello there

I m new to forum and besides chainsaws which i m excited to the mods performed by various builders i find nothing for brush cutter.

I just bought Stihl FS 560 Cem selling my previous 450 cause I needed the strongest tool available for Forest & Land clearing.

I m really curious that no mods are shown and got lot of questions.

One of them would be
1. Reason nobody mods them is the RPM limitation of the parts? (Saw cutters etc)

2. Might be limited to maximum RPM however PERFORMANCE is not only high revs but the spread of torque and hp along the useful fasma. And these beasts love torque so builders could walk that way.

Any other thoughts & suggestions?

Anything for the good and the order?

Food for thought.
 
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I can’t speak to the big brush cutters like the 560, but I just went through and did a little porting and polishing on a KM 56. Its literally half the displacement of the 560, but the same principles apply.

Once you understand the basics of a chainsaw woods port, you can generally apply them to the brushcutter engine. Port shape, port timing, squish, free flowing exhaust......

On the KM 56 I was pretty conservative, I kept basically the same timing numbers, only raised the roof of the intake a touch. I widened the intake, didn’t touch the transfers, widened and properly bell-mouthed the exhaust. The mufflers are ridiculously restricted, so I opened up the deflector a bit to basically match the size of the exhaust port. I can’t yet confirm how it runs as I am waiting on a working coil.

Hope this helps a bit
 

sawfun

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The clutch on an fs 250 was deemed too weak to handle more power according to a thread a while back. The same issue may be the case for the bigger brush cutters. My fs 550 had way more power than I ever needed, and I ran it hard (deforesting) in very tough stuff with the 4 string trimmer, saw blade, and tri tip cutter. It never slowed down, and always ran like it had no load on it. It also sure drank a ton of fuel. I figured the fs 450 might have been perfect. And I like power.
 

Evansaw

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The clutch on an fs 250 was deemed too weak to handle more power according to a thread a while back. The same issue may be the case for the bigger brush cutters. My fs 550 had way more power than I ever needed, and I ran it hard (deforesting) in very tough stuff with the 4 string trimmer, saw blade, and tri tip cutter. It never slowed down, and always ran like it had no load on it. It also sure drank a ton of fuel. I figured the fs 450 might have been perfect. And I like power.


Recently I bought ght FS560cem so I like power too!!!
 

Fairways_and_Greens

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I have the Husqvarna 345. I did some reading regarding porting clearing saws. The consensus is the drive shafts and transmissions are the weak points. I’ve seen many times that porting and muffler mods help reduce heat on here. I’m probably going to do a light port like buck wild more for letting the motor wind up a little easier. I believe that the trimmers/clearing saws seem more corked up than their chainsaw sisters.
 
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I have the Husqvarna 345. I did some reading regarding porting clearing saws. The consensus is the drive shafts and transmissions are the weak points. I’ve seen many times that porting and muffler mods help reduce heat on here. I’m probably going to do a light port like buck wild more for letting the motor wind up a little easier. I believe that the trimmers/clearing saws seem more corked up than their chainsaw sisters.

Seems to me it is more in the muffler/exhaust. Every single one I have done had a VERY restrictive muffler, especially the Echo and Husqvarna. A little bit goes a long way with them.
 

Evansaw

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Would you guys suggest I should muffler mod my 560cem?

Well muff mods are the only mods i m capable to do, even those are rarely found in my country.

Critical question: if so and need to proceed What’s the steps? Bigger factory hole? How much? Second one? Dimensions?
 
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Would you guys suggest I should muffler mod my 560cem?

Well muff mods are the only mods i m capable to do, even those are rarely found in my country.

Critical question: if so and need to proceed What’s the steps? Bigger factory hole? How much? Second one? Dimensions?

Every engine style is different. You need to do some testing and see what works best for what you want to do.

I know on the Echo trimmers I remove the hood/deflector, plate and gasket, then try to open them up to match the exhaust port of the muffler opening. The hood/deflector is an oddball style that forces exhaust to make 180* turn inside the deflector. You can’t just hack out the deflector and be done: the exhaust will blow out on plastics and other components. Need to get a little creative without going overboard.
 
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