Silencer Packing Material

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govols
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Silencer Packing Material

Post by govols »

I've just disassembled my Pro Circuit 296 silencer/spark arrester. The packing is pretty nasty and worn/torn. Other than more noise what would be the result of not re-packing the silencer...just leaving the packing material out?
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adam728
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Re: Silencer Packing Material

Post by adam728 »

Gases will not flow through a perforated tube nearly as efficiently if its surroundings are open vs covered, even with a permiable material.

In other words, it will change exhaust tuning and performance, most likely for the worse. Not to mention it will be LOUD. And our sport doesnt need more loud bikes pissing people off and closing more riding areas.

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cornishwrecker220
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Silencer Packing Material

Post by cornishwrecker220 »

A 2 stroke needs back pressure from the exhaust gasses to aid with its performance, by removing the packing or if the packing gets gummed up or has gone hard the `pulses` that travel up & back through the exhaust wont do their job as efficiently which can & will have a big effect on how your 2 stroke performs...always repack your 2 stroke silencer with a quality packing ( FMF pink string packing is excellent & seal all joints with silicone sealant upon assembeling ) atleast every 6 months for optimum performance...don't pack it in too tight though!
Deseret Rider
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Re: Silencer Packing Material

Post by Deseret Rider »

I've used stainless steel scouring pads---donut shaped--slid over the perforated tube---about 8 or nine of them----with great success in repacking mufflers. These allow gas flow through without getting clogged up with oil like the stock fiberglass blanket material----and at the same time they must provide sufficient back pressure to keep the bike running strong. In fact, I have a WR 250 (two stroke) that runs much stronger with a wider powerband than it had before. The bikes, packed in this way do not run quieter---nor do they run louder---in my experience. On my 220 KDX this method of re-packing the FMF turbine core has resulted in the bike pulling lower and into the powerband at a lower rpm and keeping the bike pulling hard farther up into the band---but I can't say one way or the other what effect it has way up on top of the RPM range because I just don't ride it up there----don't have to.
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KDXrider1989
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Re: Silencer Packing Material

Post by KDXrider1989 »

Deseret Rider wrote:I've used stainless steel scouring pads---donut shaped--slid over the perforated tube---about 8 or nine of them----with great success in repacking mufflers. These allow gas flow through without getting clogged up with oil like the stock fiberglass blanket material----and at the same time they must provide sufficient back pressure to keep the bike running strong. In fact, I have a WR 250 (two stroke) that runs much stronger with a wider powerband than it had before. The bikes, packed in this way do not run quieter---nor do they run louder---in my experience. On my 220 KDX this method of re-packing the FMF turbine core has resulted in the bike pulling lower and into the powerband at a lower rpm and keeping the bike pulling hard farther up into the band---but I can't say one way or the other what effect it has way up on top of the RPM range because I just don't ride it up there----don't have to.
+1, ive used steel wool with good results as well back then. now I just use FMF packing because I can get it for cheaper and I like the sound
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Silencer Packing Material

Post by Deseret Rider »

Just to be clear----I used the small "Scotch Bright" scouring pads----you can get them at a grocery store in Stainless steel or in Copper. They come packaged about 4 to a package and it takes two packages to do a muffler---total cost maybe about 6 bucks? I've also used fine and extra fine steel wool pads in the past but these are not 'stainless and both the fine and extra fine wool pads tend to become oil soaked and in that condition probably do not allow gases to pass through as they did when new and clean. The Scotch bright pads are much courser and tend not to clog with oil----eventually the raw oil collecting in the muffler sill start to blow out the back. When this occurs one can take the muffler down and simply wash the pads out with a soap solution ---the pads to not disintegrate as do fiberglass or ordinary steel wool. Of, simply replace them ---which is what I do because the cost of the pads isn't hardly worth the effort to wash the old ones out.

Sound issue aside----(I understand your reasoning)----I prioritize 'performance' and like the way the Scotch Brights lower and widen the powerband on my bikes---But I'm not sure that this is universal for all bikes------probably the make and models of the pipe, muffler and stinger size all play into that formula
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SPD
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Silencer Packing Material

Post by SPD »

I gave this a try after reading Deseret Rider's posts and then doing a little bit more reading on the interwebs. 9 of the SOS Stainless Steel sponges were literally a perfect fit in my Turbine Core II.

Like DR said I don't think it makes the bike any louder but maybe gave a slightly different note to the exhaust. Definitely no loss in performance at all.

Check it out for yourself:

This is with factory FMF packing that had about 900+ miles on it:


With the SS Sponge packing (5th day of riding with it in):


I had just done it as a quick fix till I got my FMF silly string, I like it enough that i'm going to keep it the way it is now.

Thanks for the tip!
GOT WOODS?
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Re: Silencer Packing Material

Post by GOT WOODS? »

Here is what I want to know: What is the magic inside of the stock KDX silencer that makes it so quiet and never needs to be repacked? I would stick mine onto the end of my FMF Gnarly pipe and ditch the TurbineCore but it won't fit. I think a crash somewhere along the way pushed the pipe back a ways and now the holes won't line up. I had been told that it is a direct swap but again, I can't get mine to fit.
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newbbewb
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Silencer Packing Material

Post by newbbewb »

cornishwrecker220 wrote:A 2 stroke needs back pressure from the exhaust gasses to aid with its performance, by removing the packing or if the packing gets gummed up or has gone hard the `pulses` that travel up & back through the exhaust wont do their job as efficiently which can & will have a big effect on how your 2 stroke performs...always repack your 2 stroke silencer with a quality packing ( FMF pink string packing is excellent & seal all joints with silicone sealant upon assembeling ) atleast every 6 months for optimum performance...don't pack it in too tight though!
funny, the FMF pink string is 4 stroke packing. I use it all day long no problem.
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Deseret Rider
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Re: Silencer Packing Material

Post by Deseret Rider »

The 'timing pulse' that bounces the raw fuel back into the chamber just before the piston closes off the port ----and the 'reverse pulse' which occurred earlier in the stroke (which pulled a charge into the chamber in the first place) is resultant from the shaping and location of the cones in the expansion chamber.
When we talk about 'back pressure' I think we are talking about that 'timing pulse'. In my view anything that interferes with those 'pulses' ---such as an additional back pressure caused by an oil soaked packing only degrades the engine performance. I think you want a free flow of gas throughout the exhaust system so that the expansion chamber works as designed. The trick is to 'silence' the exhaust without interfering with the unrestricted flow of gases out the exhaust . The selection of packing material is therefore germane to that issue. Usually 'quiet' and 'performance' are at odds with each other. FMF probably knows as much as anyone about how to get the best of both. OEM exhaust systems usually use a double wall system which makes them quiet at the expense of weight----FMF and others claim to shave weight and add performance maybe at the expense of 'silence'. What ever floats your boat.
The Duck of Deseret (Deseret was Utah's first name)
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