My first muffler mod! Tured out well!

[Mac 6-10]

I have a Husqvarna 128LD that I bought a few years ago. the only complaint I had was when you mashed the throttle it took along time to get to full power and it took alittle while to get back to full rpm after hitting something that would cause it to bog down. tried tuning it and it got better but nothing like my old trimmer. found out this model has the catalytic converter. Read on the chainsaw forum about gutting mufflers and modding them. so off the work I went. uncrimped the muffler, removed the cat, bored the ehaust port, and brazed a 5/16 copper 90 fitting in place. I must say obviously it is louder but its accereration is like a chainsaw now. just have to wait till the snow melts to find some grass to see how it performs.


Stock muffler with the spark arrestor and deflector removed showing the 3/16" stock exhaust hole.
View attachment 286617

Once the muffler is uncrimped the cat simply slides out.
View attachment 286618

The exhaust hole is reamed to 7/16 inch and the copper fitting ready for brazing.
View attachment 286624

The muffler reassembled, less cat, and new exhaust port installed on the trimmer.
View attachment 286625

 

[7sleeper]

That is a nice MM for a cat. I did a similar mod on the same typ of cat muffler. My assumption with this type of cat muffler is that the middle piece is simply encased steel wool. Because on my muffler the inside had a type of coarse metalic coating. That I believe was the ¨catalytic¨ component.

7

 

[jkarlberg]

I just did pretty much the same thing as this, the before and after results were pretty outrageous but it is loud

 

[Mac 6-10]

I just did pretty much the same thing as this, the before and after results were pretty outrageous but it is loud

It shouldn't be loud wearing your safety gear

 

[Elmore]

I recently did a MM on a little ECHO CS310, removing catayst. Next a CS400. and maybe some on a Dolmar PS401 then to a new Poulan Pro 330. The Dolmar and the Poulan likely don't have catalyst. Would like to modify the mufflers on my ECHO line trimmers but since they don't have adjustable carbs I may hold off untill I get a tool to be able to adjust their carburators after the muffler work. Performance is important but longevity and reliability are of more importance to me.

 

[Merc1973]

Old thread, but did you guys adjust the carb afterwards? Will it run too lean?

 

[Mac 6-10]

yes you need to tune it afterwards

 

[Jimmy in NC]

Any chance of getting the pictures re-posted?

 

[LinkedXJ]

^ What he said!