Gutting the Dolmar 7910 Muffler

I've had a couple of these mufflers sitting on my bench for awhile now waiting to be split and gutted. Summer is usually busy but I was prompted in the Husky 465 rancher becomes Makita 6421 thread by My IS heats my home and HDRock to carve out some time to get er done.

The title says 7910 but the 6410/6421 should have a very similar muffler. The guts of the muffler may be different but the process is the same. There are about as many ways to split the muffler on saws at there are to swing a dead cat. This is what usually works for me.

Dolmar was kind enough to leave us a nice starting spot at the top mounting hole. Heat the crimp and pry it open



I heat the crimp to just orange hot. Needless to say gentlemen the muffler will be hot at this point. Welders gloves or heavy leather gloves might be a good idea.




Pretty straight forward just pry the crimp open with whatever you have handy. I used a flat blade screwdriver on this muffler and pried the crimp open all the way to the bottom edge. From there you should be able to pry, wiggle, swear at, and eventually work the two halves apart.



Next the inner chamber (Dolmar calls this the SLR chamber) should just pull straight out. In the picture below; Top: back half of muffler, Middle: the SLR chamer, Bottom: front half


You can see here my dealers quick and dirty work around for the SLR chamber is to just drill a couple 1/2" holes into it from the exhaust port on the muffler.



After you remove the SLR chamber work the two mufflers halves back together. You may need to widen the gap on the bottom edge to make it easier to fit the back half of the muffler back into the front half.

Make sure the holes all line up and begin crimping the halves back together. You may need to hammer/peen the crimp back over slightly to get it to roll back over. I use channel lock type pliers to roll the crimp back together. Heat may make this easier but I usually just cold roll it.



I like to start at the top and work my way back down to the bottom edge.



And there you have it the finished product. All this only took about an hour to do. Hope this helps fellas.

 

Good info barcroft b, very nice descriptive easy to understand thread.

 

Thanks Brad
Nice write up, pictorial how to.
What do you do, clamp it in a vise just enough to hold it without crushing it?

 

Exactly so clamp it in a vise. They are pretty tough.

 

So to the experienced this is a dumb question, but doing this gives you extra horse because it can breathe better, but it requires the saw to be re tuned correct? Would this be worth doing on a husqvarna 445? It's a little short on power for me.

 

Good stuff. But...... how's it sounds. Before and after video would be awesome, just after video would be good. Lol

 

Most saws wake up after having a muffler modded. I've heard the muffler on the 445 is actually some sort of aluminum alloy. Think pot metal which doesn't tend to like to bend without breaking. Gutting the muffler in this manner might not be that easy. I couldn't say because I've never done one.

 

pizz rev video junky!

 

Well ya but we don't use the word junky anymore. (Politically incorrect)
I have an entire Playlist on YouTube of just pizz revving! Lol

 

I have a 445 and I am sure it will wake up. Every saw u have has responded. You can use a drill and drill in through and or DreMal through the inlet for the muffler. And cut and remove stuff. And then make the exit port larger and you can do a quick dirty muffler mod. Or just drill a hole from back too front if you like. These are not as clean and more of a hack job but it's an option for a quick muffler mod. You can always buy a china muffler off ebay and hack it up if your worried about you factory one. And often the china mufflers are just straight through cans. And you can just open up the exit hole larger.

 

I think maybe you meant to quote shaggy wood dump hoarder horder here right Nate?

 

Yep.

 

I see you skating there on the thin ice. I'll throw ya a line. How about mainliner, addict, fanatic? Take your pick.

Truthfully I don't have a before video of this muffler. I doubt it sounds better than the dual port thats on the 7910 now!



My apologies for the punky beech it's all I had on short notice.

 

Or the saw is slow or the camera have problem ........................................ ok i make fun

nice saw man

 

Thanks bud. More torque than speed with this model which is just the way I like em!

 

Sounds good!

 

Nice right up Barcroftb. I may have missed but I do mine almost exactly the same but the flange around the slr unit is reinstalled I cut the couple tac welds off. Throw slr in trash and reinstall the flange.

 

Does that tube go into the cylinder? What side of the muffler is this picture? Does that go to the cylinder side or the muffler side?

 

Man Carl I must have spaced out when I wrote that up. I did cut all the extra "stuff" off the flange and put it back in as a spacer. Nice catch buddy!