Need help with a muff mod! Can't get a Husqvarna muffler uncrimped.

[shorthunter]

Gonna be tough with a backpack blower....

I thought we were talking chainsaws here. With a blower you could use a wind vane at a measured distance to see what your maximum air velocity would be before mods and after mods

 

[ANewSawyer]

There we go. I like you people because you are practical!

 

[Chris-PA]

I thought we were talking chainsaws here. With a blower you could use a wind vane at a measured distance to see what your maximum air velocity would be before mods and after mods

With a blower (and to some exent a string trimmer) you have a very non-linear load. The resistance will just become a brick wall at some point, requiring a huge increase in power to spin it faster. If you've ever used a bicycle fan trainer you would have a good feel for that. So it would be hard to get a good measurement of the small differences of various muffler mods. It essentially has a max rpm limiter on it.

A chainsaw is a sifferent kind of load, but there you have variations on the wood, chain sharpness, etc.

 

[shorthunter]

If the blower is governed to a certain RPM and you are already running at that RPM, then there would be no point in doing a muffler mod. Engine RPM, fan speed, CFM and velocity are all directly correlated on a blower.

I would think a person could increase engine speed (RPMs) by opening up the muffler and adjusting the carb. This would in turn increase fan speed and CFM

 

[Big_Wood]

Ok, well, I ain't worried about it.

Muffler pics! Some of the grinding wasn't the best but not bad for a first time grinding with a hand held angle grinder.

Front so you can see where the deflector goes.


Split.


The metal in the box is going away. Deflector screws into the front of the muffler over this port.

is that all that was inside that muff? heck i wouldn't have even considered splitting that. cut hole bigger from the outside, flush it out, paint, and done.

 

[ANewSawyer]

No, there was a lot more! A big ole cat jumped out at me. Sadly, it was lost while attempting to bring the muffler in the house. A moment of silence for all the lost cats in the world...

 

[Big_Wood]

A cat muffler and the lack of AM open can replacements are about the only reason why I'll ever split a muffler.

 

[Chris-PA]

Here kitty kitty kitty......

 

[ClemsonEngineer]

I split the muffler on my 128LD 2 days ago. It runs so much better now that I removed cat and opened exit hole. I also re-shaped the deflector that holds the spark arrestor on. I did not reinstall the spark arrestor. I used a screwdriver to un-crimp exhaust and re-sealed with black rtv and re-crimped with needle nose pliers.





This picture shows the size of the new exit hole relative to the inlet hole. The exit hole is behind the inlet hole. It is definitely less than 85%
I bent the deflector to allow more air flow. I also removed some of the metal from the plate inside the hole in the deflector plate (made edge of deflector plate inside opening into an arc)

For more pictures see the link below:
https://www.dropbox.com/sh/e9dq56puf2izew9/AADCJfQa8GYFjokI0FsCDlJka?dl=0

The trimmer runs way better now! The throttle response is perfect. I still have it adjusted a bit rich because it is still breaking in (moded it after only running it through one tank of fuel). Once it has run through a few more tanks of fuel I will probably lean out the mix a little more. I plan to leave it a little bit richer than optimum for long term reliability. Words cant describe how much better this trimmer is without a strangled exhaust.

 

[ANewSawyer]

Glad to see yours went off so well. Mine is welded back together and back on my 125B.

 

[bikemike]

Jughead has done done some work on the 435 I think. I may drop him a line. Thanks for the help. I didn't realize my 435 was a strato.

The 125B that I am also working on does not appear to be strato and the muffler is full of cat.

Yeah get rid of the cat asap