Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
BCM
User Panel

Site Notices
Posted: 2/15/2017 2:17:52 AM EDT
So, one of my chainsaws (Husqvarna 575XP) went down the other day while cutting a few trees.  At first, it seemed like the muffler had just loosened, so I grabbed the 372XP to finish.  Got the saw home to tighten the muffler bolts, and realized the lower tabs had both cracked completely off.  Seems like the top two bolts that attach the muffler to the exhaust port loosened, and vibration eventually caused the lower support tabs to shear off.  





Easy fix, right...just order a replacement muffler.  Nope.  Because the 575XP wasn't a very popular saw, aftermarket parts are basically non-existent.  As such, muffler is $70 (372 is under $30).  I'm too cheap to pay that much, so decided to give it a go at fixing it myself.  

First order of business, exhaust gasket is trashed...



...and the exhaust side bolt holes have egged out a bit.  I am not sure how much an issue this is, as I am sure the holes help correctly orient/locate the muffler to the cylinder head.    



Here's the muffler.  The broken tabs also left holes into the body of the muffler, which has to be fixed before anything else can be done.  




Here's the problem.  The shell of the muffler is very thing gauge steel, and welding up is just about out of my skill set.  Nevertheless, I didn't let it deter me.  Here they are cleaned up...






I initially considered trying to TIG weld them up.  I have two nice TIG machines, but my skill as a TIG welder simply doesn't match either machine.  I was nervous about trying it, so I stuck with my smaller MIG...a Lincoln Pro MIG 140 with .023" solid wire and 75/25.  Plus, the TIG welders require getting out the torch, foot pedal, grinding tungsten, etc....and my MIG was just sitting there all ready to go.  






The phrase "bird poop" comes to mind, but welding thin stuff with a MIG isn't always easy.  The trick is to keep the heat on the previous weld, and let the "pool" extend to the thin stuff (at least that's my understanding).  You can only do quick spot welds, otherwise you get a big ass hole...which is what kept trying to happen anyway.  It doesn't take much to burn through, but I eventually got both welded up.  Oddly enough, the first side looked a lot better than the second.  I didn't mind building it up a little thick, as it would give me some "meat" to weld a new tab to.  

Here they are contoured back down...




...and fitment checked...





Clearance was OK, so I went to fabbing up a piece to weld to the bottom of the muffler to act as the lower support.  I didn't take any pics of making the piece, but it took a decent amount of time on the belt sander to get it shaped correctly.  Drilling the holes was the hardest part, there was really no way to make sure they were correct.  Luckily, they turned out perfect.  I bolted the muffler in place, and then the lower support tab, and then tacked them together....which was  PITA as there is absolutely no room.  I finally got it tacked, and then welded it up with a series of spot welds.  






Once again, I had to be very careful not to burn through the muffler itself.  I thought I had some high heat black paint, but turns out all I had was red caliper paint...its currently drying.  I'll post a few pics once I get in back in place, after I get a new exhaust gasket.  

Not the prettiest welding I have done, but good enough for the job at hand!
Link Posted: 2/15/2017 2:32:31 AM EDT
[#1]
Link Posted: 2/15/2017 2:35:23 AM EDT
[#2]


Nice save!!

Brazing works pretty well for those jobs, but welding works better.

The 576XP muffler is a 1-1 match IIRC. Baileys, and several others carry aftermarket units.

While in there, ya shoulda Modded that muffler. The 575 wakes up a good bit, with a less restrictive muffler.

I use BBQ paint, but don't care if it doesn't look factory....and I suppose any color works.
Link Posted: 2/15/2017 2:45:54 AM EDT
[#3]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Nice fix, but you shoulda bought a Stihl.  
View Quote


My 28" bar is on a Stihl 460...
Link Posted: 2/15/2017 3:20:11 AM EDT
[#4]
I would have welded the flange to a straight pipe. Muffler lol, hearing is for suckers!
Link Posted: 2/15/2017 3:38:32 AM EDT
[#5]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I would have welded the flange to a straight pipe. Muffler lol, hearing is for suckers!
View Quote


You know, I actually considered this.  I just don't know enough about the science of 2-stroke mufflers, and was afraid I'd end up burning a hole through the piston.
Link Posted: 2/15/2017 3:54:41 AM EDT
[#6]
Like a boss,, you would fix right in here.....welcome to the fix the damn thing .  over paying overpriced parts
Link Posted: 2/15/2017 4:06:12 AM EDT
[#7]
You would fit in in Alaska.  DIY fast

ETA yes, Stihl
Link Posted: 2/15/2017 4:09:27 AM EDT
[#8]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


You know, I actually considered this.  I just don't know enough about the science of 2-stroke mufflers, and was afraid I'd end up burning a hole through the piston.
View Quote
It won't hurt the piston, just make the saw run like shit.

Without some back pressure you will lose part of your charge and a shittone of powerpower.
Link Posted: 2/15/2017 4:43:17 AM EDT
[#9]
Without some back pressure you will lose part of your charge and a shittone of powerpower.
View Quote


That's the trick, how do I figure out how much back pressure is necessary?
Link Posted: 2/15/2017 7:05:31 AM EDT
[#10]
Looks good enough for me. I silver braze stuff like that but not too many people know how to do that.
Link Posted: 2/15/2017 7:36:22 AM EDT
[#11]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


That's the trick, how do I figure out how much back pressure is necessary?
View Quote


NO.

That is not the trick.
The first way to tell someone knows nothing about exhaust systems is to hear that old "needs some backpressure" wives tale.

A two stroke uses the momentum and timed expansion of the exhaust as part of the intake cycle.

You need a correctly shaped bubble in the pipe, the right distance from the exhaust port in the cylinder.  

"Short and fat" is the OEM muffler/expansion chamber design, mounted close to the head.

Move it farther from the head will make power sooner,
A bigger chamber may help (muffler cavity).
A less restrictive to flow muffling section will help.
Changing the chamber taper (both inlet AND/OR outlet) can change the width of the powerband.
Link Posted: 2/15/2017 8:04:28 AM EDT
[#12]
yeah, I've ported a few saws, and gutted mufflers, and I would not have gone that far. but if it works, who cares.
Link Posted: 2/15/2017 8:22:57 AM EDT
[#13]
Nice repair job!
Link Posted: 2/15/2017 9:21:05 AM EDT
[#14]
Did you heat up the weld area with a torch after the weld?

I'd be concerned about the thin metal hardening at the welds which will cause further cracking in the future.

(Not a welder and I did not sleep at a any hotel last night)
Link Posted: 2/15/2017 9:47:31 AM EDT
[#15]
Hope you don't weld as a profession

Good job on the fix. Try brazing it next time.

Ed
Link Posted: 2/15/2017 9:51:29 AM EDT
[#16]
Fail.  Should have added whistle tips.
Link Posted: 2/15/2017 9:54:39 AM EDT
[#17]
Run my STIHL saws hard and no muffler issues.
Link Posted: 2/15/2017 9:57:55 AM EDT
[#18]
Whistle Tips go, "WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO"
Nice repair.
Link Posted: 2/15/2017 10:15:14 AM EDT
[#19]
I'd be concerned about the thin metal hardening at the welds which will cause further cracking in the future.
View Quote


I considered this, and would not be surprised at all if it doesn't eventually crack.  However, as long as the bolts stay tight, shouldn't be an issue (I hope).  The original failure was simply because the cylinder head bolts loosened up, allowing the muffler to vibrate enough to fracture the lower tabs.  

Run my STIHL saws hard and no muffler issues.
View Quote


This is the first muffler issue I've ever run into with any saw, Stihl or Husqvarna (and I have owned a lot of them).
Link Posted: 2/15/2017 10:18:38 AM EDT
[#20]
A two stroke uses the momentum and timed expansion of the exhaust as part of the intake cycle.

You need a correctly shaped bubble in the pipe, the right distance from the exhaust port in the cylinder.

"Short and fat" is the OEM muffler/expansion chamber design, mounted close to the head.

Move it farther from the head will make power sooner,
A bigger chamber may help (muffler cavity).
A less restrictive to flow muffling section will help.
Changing the chamber taper (both inlet AND/OR outlet) can change the width of the powerband.
View Quote


So, without overly complicating things, how would I go about fabbing up a muffler shape that would optimize performance of the saw (and be less restrictive than the factory)?
Link Posted: 2/15/2017 10:21:20 AM EDT
[#21]
I don't know if they would have it or not but I've used Jack's small engines for parts in the past.
They have all kinds of crazy stuff that is hard to get.

PS: They have awesome exploded pics too
Link Posted: 2/15/2017 10:38:41 AM EDT
[#22]
Good job.

If it fails, a new muffler that fits is  $35 on Amazon prime.

https://www.amazon.com/Husqvarna-Part-Number-544030201-Muffler/dp/B013WPVMBA?tag=vglnk-c102-20
Link Posted: 2/15/2017 10:53:43 AM EDT
[#23]
Whatever works.

The exhaust manifold/header on my old Jeep Cherokee 4.0 cracked on me one time and I didn't want to shell out $250 for a new one.

We welded that bitch up .35 fluxcore and packed it with muffler putty. I drove it about 6 more months and sold it.
Link Posted: 2/15/2017 11:32:58 AM EDT
[#24]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


So, without overly ;complicating things, how would I go about fabbing up a muffler shape that would optimize performance of the saw (and be less restrictive than the factory)?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
A two stroke uses the momentum and timed expansion of the exhaust as part of the intake cycle.

You need a correctly shaped bubble in the pipe, the right distance from the exhaust port in the cylinder.

"Short and fat" is the OEM muffler/expansion chamber design, mounted close to the head.

Move it farther from the head will make power sooner,
A bigger chamber may help (muffler cavity).
A less restrictive to flow muffling section will help.
Changing the chamber taper (both inlet AND/OR outlet) can change the width of the powerband.


So, without overly ;complicating things, how would I go about fabbing up a muffler shape that would optimize performance of the saw (and be less restrictive than the factory)?
Guy explained it perfectly, short version is modifying the muffler will likely cause a drop in performance and could smoke the piston
Link Posted: 2/15/2017 11:44:11 AM EDT
[#25]
Ehhhh JB Weld...
Link Posted: 2/15/2017 11:48:54 AM EDT
[#26]
I no longer feel bad about my welding skills.
Link Posted: 2/15/2017 7:15:57 PM EDT
[#27]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Good job.

If it fails, a new muffler that fits is  $35 on Amazon prime.

https://www.amazon.com/Husqvarna-Part-Number-544030201-Muffler/dp/B013WPVMBA?tag=vglnk-c102-20
View Quote


Awesome, thanks!!
Link Posted: 2/15/2017 7:19:55 PM EDT
[#28]
Damn, I'm a shitty welder but....
Link Posted: 2/15/2017 7:22:52 PM EDT
[#29]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I no longer feel bad about my welding skills.
View Quote


Hey, if you're better at welding thin gauge muffler housings, feel free to post pics... ;)

I think I'm going to spend a little time with the TIG, and see if I can't get a little better on thinner stuff.  I'd gotten where I could do 1/8 without too much trouble, but the really thin stuff is more of a challenge.  I know some guys TIG razor blades together, I'm no where near that....yet.  :)
Link Posted: 2/15/2017 7:23:18 PM EDT
[#30]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I no longer feel bad about my welding skills.
View Quote


Hey, if you're better at welding thin gauge muffler housings, feel free to post pics... ;)

I think I'm going to spend a little time with the TIG, and see if I can't get a little better on thinner stuff.  I'd gotten where I could do 1/8 without too much trouble, but the really thin stuff is more of a challenge.  I know some guys TIG razor blades together, I'm no where near that....yet.  :)
Link Posted: 2/15/2017 7:29:46 PM EDT
[#31]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


I considered this, and would not be surprised at all if it doesn't eventually crack.  However, as long as the bolts stay tight, shouldn't be an issue (I hope).  The original failure was simply because the cylinder head bolts loosened up, allowing the muffler to vibrate enough to fracture the lower tabs.  


This is the first muffler issue I've ever run into with any saw, Stihl or Husqvarna (and I have owned a lot of them).
View Quote


If you start to see a hairline crack, drill a hole at the end of the crack to stop it from spreading. Cracks in sheetmetal are like the little cut in the side of a packet of ketchup. If you drill a hole at the end, it'll require a lot more force for it to spread. Very common in aviation.

Link Posted: 2/15/2017 7:33:07 PM EDT
[#32]
Ear plugs with ear muffs over them. Problem solved.

Or is venting hot exhaust an issue where it can hit/burn you with the muffler crack?
Link Posted: 2/15/2017 7:41:10 PM EDT
[#33]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Ear plugs with ear muffs over them. Problem solved.

Or is venting hot exhaust an issue where it can hit/burn you with the muffler crack?
View Quote

yeah, front muffler on a husky, the wrap around hand guard is right above that thing. Plus, you want a spark arrestor of some sort to avoid fires.
Link Posted: 2/15/2017 9:34:45 PM EDT
[#34]
If you start to see a hairline crack, drill a hole at the end of the crack to stop it from spreading. Cracks in sheetmetal are like the little cut in the side of a packet of ketchup. If you drill a hole at the end, it'll require a lot more force for it to spread. Very common in aviation.
View Quote


I think I am going to go ahead and order the replacement linked above, and keep it in case this one doesn't work out.  If I had known I could get one for $35, I would have never spent the time fixing this one!

Of course, if I order a replacement, then it means this one will last forever!
Link Posted: 2/15/2017 11:00:18 PM EDT
[#35]
Here's the finished product.  I'd considered painting the entire muffler red, but wasn't sure how well this paint would hold up.  Fit up looks good, but won't be able to actually run the saw until I get a new exhaust gasket.




Close Join Our Mail List to Stay Up To Date! Win a FREE Membership!

Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!

You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.


By signing up you agree to our User Agreement. *Must have a registered ARFCOM account to win.
Top Top