Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Dolmar Makita => Topic started by: pigpen60 on September 12, 2014, 05:46:09 pm
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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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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.
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I heat and roll it up with a screw driver.
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don't use a good screw driver though
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grand kids are here for weekend. will get back to work Monday!
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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.
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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?
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7900 is the same
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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.
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how much do I open the stock exit? is this muffler stainless steel?
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I didn't touch the original opening. I just made a new one in the front to get the exhaust out faster.
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Looks and welds like aluminized steel. I opened my last 7900 muffler exit to approx 75% larger Area.
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It's magnetic. I didn't do any welding on this one. Just crimped it back.
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Probably better to unfold/crimp. One I just did recently was a mess Tig welding even after cleaning off the aluminum coating carefully
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I figured it would be so I just tried to not damage the crimp.
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I peeled the crimp. didn't think about aluminized steel. so is there a standard exit hole ratio or such? the cat in mine looked like a kid did it, no offence to kids that can weld. my thought was to make the in and out the same size but my lack of knowledge on 2 strokes and cash is holding me back.
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Gonna be offensively loud at 1 to 1 ratio for a work saw.
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I ran a 30cc model airplane engine for a couple hours one day with no muffler. My ears were messed up for a couple days.
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ok, well if I leave the in and out the same as stock and just remove the cat I should be breathing better. correct?
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Removing the catalytic part from the muffler does away with a lot of heat and weight.
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well I had a hell of a time getting that cat outta there, ended up taking a body saw and cutting it out. all back together no extra openings and no screen. not sure if I should put the screen back. seems louder. I almost windowed all the inside sections so they were just frames but I resisted. started it without bar, bar oiler works!
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You can window the baffles next time
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well I had thought I could do like someone suggested and drill a extra exit in the front cover.
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I'm assuming you cut out the baffle and left the spacers?
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the only thing I cut out was the cat and a large portion of the sheet metal it was attached to.
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My bad. Had an image of non - cat muffler in my head