I got a nice shiny new one, I would like to see pics and here info on the pro and cons on the mods. I want to open the muffler maybe a double barrel setup! Who can do the muffler for me? What kind of cost does the muffler mod cost???
Got any pics??
P.S I did search and found some good stuff but i am sure there is more
A 7900 muffler mod is very easy to do. (Much easier then a 5100 due to the shape of the muffer).
Remove the muffler and gradually open up the crimp on the bottom edge. Start in the middle because that's where it peels easiest and gradually peel open the crimp until you reach each corner on the bottom edge only.
No need to uncrimp any further because now you can slide both halves apart. Squirt some WD40 or oil into each remaining crimp so they slide appart easier. (both side edges and top edge).
Now whack the top half of one half of the muffler with a rubber mallet and it'll gradually slide down the side crimps and seperate. You won't dent the muffler if you go fairly easily.
As for the muffler, I just removed the end piece of the baffle that redirects the exhaust down 90 degrees. I also expanded the exit hole about 50-75% using a Dremel tool. The spark arrester screen will still fit.
Now slide the two halves back together and recrimp the bottom edge with a vise.
Once you reinstall the muffler there will be no evidence that the muffler was ever modded since it sits in a pocket and the lower edge doesn't show.
I should have taken pics but didn't. I'm sure a dual port mod would yield a little more performance but it's alot more involved and not invisible.