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Dirtbike muffler welded onto milling setup: Instructions

Blue42

Blue42

ArboristSite Member
Joined
Mar 19, 2020
Messages
70
Location
Maryland; southern
Gentlemen, I'm finally getting to this now so that anyone who wanted to could take advantage of the work. I've had it on my to-do list to post this for a while.

I have a Husqvarna 395XP and wanted to make it quiet. I spent about X,000 hours trying to find information on how to do it (which basically no one has done before that I found on the web) thinking about how to do it, searching for parts, and putting it together. And it works. It has made the saw quiet enough that I can start it and rev it in a closed garage and still talk comfortably to someone, and I can adjust the cutting depth from 0" up to about 9" (the flexible pipe and bolting the muffler so that it swivels is key to this). I still wear ear muffs when I do milling, but I'm in a neighborhood where I don't want to make a big racket for hours on end and attract attention, and possibly attract complaints from the homeowners association. If you're in a situation where you want or need quiet, it's worth it. But it takes a long time to do, it makes the already heavy milling rig heavier still, and it's prohibitively difficult to get the saw out of the rig, because it means detaching the exhaust too.

I'm posting pictures and parts list below.

PARTS
1) 1 1/4" OD flexible stainless exhaust tubing
. https://www1.mcmaster.com/5241K15/ (This is the key item, and the hardest to get right. This stuff does bend, even though it says "rigid" on McMaster. This is stainless also. But if you could find it in regular steel, I would do it. Working with stainless is difficult.)
2) About 3' of 1 1/4" tubing, 16 gauge (exhaust for cars and everything is normally 16 gauge; which is 0.063" = 1/16". https://www.amazon.com/gp/product/B002VRAVS6/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
3) A pre-bent piece of stainless https://www.amazon.com/gp/product/B00JB5AFTQ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 (This is the piece you attach the flexible part to. Makes the job a lot easier.)
4) A set of elbow pieces (although you should only need 1) https://www.amazon.com/gp/product/B07XXV132H/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1 (These make the job a lot easier.)
5) A 1/8" thick (or thicker; this piece needs to be sturdy) piece of stainless for the flange that bolts directly to the exhaust port on the saw https://www.amazon.com/gp/product/B07R4377L2/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1 (If I had it to do again I would probably go thicker on this piece.)
6) A used or new dirtbike or ATV muffler. I spent way, way too much time reading dirtbike forums to find the quietest muffler. I used the KTM "hockey stick." It's known for being quiet. Got one used of Ebay. The input tube is 1" OD, and the flexible pipe mates to it too loose, but I put some high temp RTV in there and put an exhaust clamp on it, and it doesn't leak.
7) Hardware: Bolts and nuts, hose clamps to hold on heat wrap, etc. Note, you'll have to do a little bit of grinding on the nuts probably to get them on past the pipe.

INSTRUCTIONS
Flange: You will want to pull exhaust gasket out and trace out the mating surface and the holes on paper, . You'll have to cut a flange out in just that shape to mate to the saw exhaust port. This was quite a pain with the stainless. I learned just how hard the stuff is. But you don't want to go any thinner than 1/8" thick on the metal. You might even want to go thicker. Mine broke once. It also bent while I was welding it. I would go to 3/16" if they have it. Or even 1/4". Drill some holes in it and get the hack saw, carbide burrs, and files going on it.

Mating pipe to flange: The exhaust port is an oval. I measured it carefully, and the ID is about 1.115". The 1 1/4" pipe matches up just right. But you have to crush it with some artistry to get it to match the shape of the port. I did pretty much all of this in the vise, but I did use vise grips, etc to massage parts. The pipe is tougher where the seam is where the weld it together, and this made it harder to do this step. And, again, stainless is not the way to go I think. I would do regular steel if I had it to do again.

Weld on the pipes: Measure how long your pipe needs to be to go straight out from the port, to clear the front of the saw. From there you'll weld on one of the small elbows. You will weld the pre-bent piece to that elbow. You don't want to go too far out from the saw, because any distance you go out too far is distance removed from how thick of a slab you can cut. I cut mine about 1/8" or so too short.
General notes
At this point I'll drop the attempted pseudo step-by-step and just describe it. Depending on what muffler you get, you will need a different length of the flexible pipe. At first I used pipe clamps on this at both ends. But then I just welded it to the pipe closest to the saw. I think it had slipped when I adjusted the height of the cut while I was milling, so that drove me to weld it. (I have a MIG welder. And I'm not good at using it at all. I had to use a grinder and carbide burr a lot to clean up the flange and the welds.)
You will need the muffler to move when you adjust the height of the cut. When you make a deeper cut, it turned up, and the hose bends. You will have to help the hose bend. It isn't floppy.
I got some of the fairly expensive exhaust wrap from Autozone. I recommend not getting the cheap stuff off Amazon. It fall apart if you touch it. Although the expensive stuff has come apart in a couple places too, from barely being touched.
At first I also wrapped the whole thing in silicon rubber I got from McMaster, with the goal being making it even quieter. But it melted a little bit and stank, and it was bulky, and I don't think it made it noticeably quieter. And it still got hot enough to burn you.
I also put a bent piece of silicon pipe on the end of the muffler to further quiet the saw. Which it did. There used to be a thing for people who really wanted quiet dirtbikes called a "dB Snorkel." They stopped making them and it's impossible to find one anywhere now. At first I just put on the most bent and twisted piece of heater hose that the auto parts store had, but it burned and smoked. It won't take the high temperatures. Then I put on a right angle piece of silicon I got for about $15. It got crackly and tore due to hard use in the woods and hitting stuff.
 

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frank_

frank_

ArboristSite Guru
Joined
Nov 5, 2019
Messages
900
Location
b/ham uk
i often use some cotton rag on the exhaust exit (rolled in a ball) to muffle a saw when ragging it in my workshop, its very effective for 10 seconds or whatever
so i would probably have welded a small end can like this, to the stock silencer personally

s-l1600 (36).jpg
 

J D

ArboristSite Guru
Joined
Apr 19, 2020
Messages
599
Location
NZ
Cool concept, long term I'd be a little concerned about the extra stress on the exhaust mount area
 
frank_

frank_

ArboristSite Guru
Joined
Nov 5, 2019
Messages
900
Location
b/ham uk
here,s my 4mix muffler, alloy skin wrapped around the stock silencer, with 6 layers of exhaust wrap trapped underneath

WP_20141201_22_12_29_Pro.jpg
 
Blue42

Blue42

ArboristSite Member
Joined
Mar 19, 2020
Messages
70
Location
Maryland; southern
Cool concept, long term I'd be a little concerned about the extra stress on the exhaust mount area
Yep. That has been a concern. If that magnesium exhaust flange on the case cracks, I'm out of a saw. So far so good. I've milled about 400 board ft with it so far.
 
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