Makita 6421 Muffler Mod With Pics

[Yotaismygame]

I haven't seen many threads with pics about Makita mufflers. There are a few youtube videos that are quite helpful.
Shortly after picking up a Makita 6421, I added a Big Bore kit with some port work done to it, and although the power increase was noticeable, it was still lacking.

Taking apart the muffler is quick and easy, if you grind off the crimped edges with a bench grinder. Throw away the whole center section, it weighs just as much as the modded muffler, cut out the deflector, and weld it back up. I also went ahead and enlarged the stock port, kept the screen, and then added another port. Welding it back together wasn't the easiest with my mig. I was near the limits on the low side for my welder. After a quick run over with a wire cup wheel she shined up real nice. Would love to keep it that way but it'll definitely rust. I sprayed it down with some high temp paint. Not really sure it'll hold up all that well but it sure looks good.

All in all i'm very pleased with the end result. The saw doesn't sound plugged up anymore, my throttle response improved a lot, and it's not all that much louder. Hopefully this weekend ill be able to make some test cuts with it.

 

[Deleted member 149229]

Looks good.

 

[Adirondackstihl]

This one is gutted too

 

[Brazos]

I have the same saw. What are the two astrik looking plugs for? Mine tend to want to pop out at times and wonder if I actually need them. You guys obviously put them back in after the muffler mods.

 

[Adirondackstihl]

I have the same saw. What are the two astrik looking plugs for? Mine tend to want to pop out at times and wonder if I actually need them. You guys obviously put them back in after the muffler mods.

Stretch the tabs out a bit.....should make for a tighter fit.
They’re just to keep sh!t from getting in the tube

 

[Yotaismygame]

This one is gutted tooView attachment 645999

Do you feel like that little extra opening is enough? Even the stock opening isn’t very big. Has it been polished like that for awhile? Has it rusted?

 

[Adirondackstihl]

Do you feel like that little extra opening is enough? Even the stock opening isn’t very big. Has it been polished like that for awhile? Has it rusted?

The stock opening has been enlarged to its fullest without exceeding the deflector. Been polished for a few months so far. Shouldn’t rust, it’s stainless....although I’m not sure of the grade, it may contain small amounts of carbon and may grow a small amount of surface rust, but I doubt it.
The saw doesn’t get much run time. Mostly GTG’s.
Mastermind ported it a few years ago. I’ve only put maybe 5 tanks through it since.

 

[chipper1]

Great work Yota, and sweet saws guys.
I've got some, two with the mufflers done, here's the pretty one, the others a worker, the rest well it doesn't hurt to have extras right .
Sorry you can't see the muffler well in this picture, maybe I'll get another later.

 

[mettee]

For those who mod these dolmar mufflers use map gas and get it cherry red, then it's super easy to use a big screw driver to bend up the crimp. Mine came out super smooth.

Getting rid of this.

I'll be adding another outlet that retains the screen. I'm also going to flip the diverter over so it dumps down not up. And I'll increase the size of it also, maybe drill some larger holes. I am also going to retain the rear most center section so that there is a good heat barrier.

 

[mettee]

I was going to add..

Leave the muffler apart if you are porting the saw. That will allow you to bolt up the back section and port match it, the shield, and the gasket.

Once you are done put the muffler together however you chose.

 

[mettee]

 

[Yotaismygame]

Not my style, but to each there own

 

[mettee]

Not my style, but to each there own

It will look a little different when its done. I want it to appear stock and have the same screen.

On the inside I am doing something a little different. I will be able to test it before I crimp the sections back together.

Haters gonna hate

 

[Yotaismygame]

Here's another way to do the 6421 muffler if you have access to a welder. This mainly applies to the 6421 only. The 6401 is much easier to pry apart with heat or not compared to the 6421.

I ground the bottom lip off, and then rotated the back part of the muffler so it would nearly come right apart. With a little pressure you can pry it apart very easily. Work your magic on the inside then repeat in reverse order. I ground the back portion of the muffler down just a touch more than the front to make welding easier.

 

[Yotaismygame]

@Dahmer You should post up a pic of that sexy muffler you have on your Makita.

 

[Yotaismygame]

Here's a 7901 muffler I did. Single 1" pipe in the stock outlet location. This saw sounded amazing. I forget who I sold it to but he's a member on here.

 

[Brent Nowell]

Dang that looks good.

Some of you guys seem to run a screen and hole in the front, aren’t you worried about cutting off flow every time you buck a log?
Shooting a pipe out the side seems to be the best choice imo .

 

[Yotaismygame]

One time I tried the hole and screen out the front on a 372 and that thing shot sparks like crazy. I added a deflector right away.

 

[Deleted member 149229]

@Dahmer You should post up a pic of that sexy muffler you have on your Makita.

 

[chipper1]

@Logger nate you should post a picture of yours for another option.