Author Topic: makita 6421 muffler mod  (Read 638 times)

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Offline pigpen60

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makita 6421 muffler mod
« on: September 12, 2014, 05:46:09 pm »
ok I took the muffler off the mak the piston looks smooth. now my Q is the cat muffler, is it stainless? how's the best way to get to the cat? and while I'm in here if I open the exit how big should I go? and last if I go to 7900 is the opening the same?

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Offline Nathaniel Vansickle

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Re: makita 6421 muffler mod
« Reply #1 on: September 12, 2014, 06:10:41 pm »
2 ways to open the muffler up. 1st is grind the seem off and open it up then braze it back together. 2nd is heat up the crimp with a torch and use a screwdriver to open up the crimp on 3 sides. putting it back together is just heat it back up and bend the crimp back down.

don't open up the outlet to much or it just makes them louder.

picture is of a 5105  muffler but you can see how the crimp is opened up on 3 sides. takes some time to do a nice job and be careful not to melt the muffler when you are heating it up.
im sure there are other ways to do this. I heat the crimp up on all the ones I do but have seen lots of the cut and braze method.
5105H and 6400H in stock

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Offline mdavlee .

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Re: makita 6421 muffler mod
« Reply #2 on: September 12, 2014, 07:09:41 pm »
I heat and roll it up with a screw driver.

Offline Nathaniel Vansickle

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Re: makita 6421 muffler mod
« Reply #3 on: September 12, 2014, 08:08:23 pm »
don't use a good screw driver though
5105H and 6400H in stock

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Dolmar, Echo, Jonsered


Offline pigpen60

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Re: makita 6421 muffler mod
« Reply #4 on: September 13, 2014, 04:15:53 pm »
grand kids are here for weekend. will get back to work Monday!

Offline mdavlee .

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Re: makita 6421 muffler mod
« Reply #5 on: September 13, 2014, 04:27:51 pm »
I used a scrench. It took a few minutes to get it rolled back to where it would come apart. I cut the cage out except where the tubes meet the mounting flange.

Offline pigpen60

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Re: makita 6421 muffler mod
« Reply #6 on: September 13, 2014, 08:21:34 pm »
ok had a moment, opened it up. leave the cage connected to the tubes the screws go through, correct? take cat out. later I would like to use this saw on a chainsaw mill, so any advice on exit opening? I had thought about welding original open closed and maybe moving exit to the front somewhere with a deflector.  I measured the opening in the jug as 1.125x .558(1 1/8"x9/16") small error due to radiuses. is this sound right? also 7900 is it the same?

Offline 660magnum

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Re: makita 6421 muffler mod
« Reply #7 on: September 13, 2014, 08:27:08 pm »
7900 is the same
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
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Offline mdavlee .

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Re: makita 6421 muffler mod
« Reply #8 on: September 13, 2014, 08:40:51 pm »
I took the cage out except the part at the flange where the tubes go on the last one I did. For milling the stock opening is going to be better than putting it more towards the front. The 395 I use will get the mill so hot you can't touch any of it without leather gloves. A straight out the side exhaust is best for a mill.

Offline pigpen60

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Re: makita 6421 muffler mod
« Reply #9 on: September 14, 2014, 11:04:28 am »
how much do I open the stock exit? is this muffler stainless steel?

 

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