7910 muffler mod

I'm getting ready to do a build thread on a 7910 but ran out of parts for the saws I'm working on now. So I decided to go ahead and MM one of the 7910s. Here's what I got. I heated up and uncrimped the muffler seams. And the first pick is what you see when opened up. And i forgot to take a pic of this so I stole this one from mastermind. Lol. I took out the expansion chamber looking thing(SLR) and cut the flange off of it and ground it to match the muffler inlet. Then tacked it to the muffler. This is for support and spacing. The outlet had a factory stamped pattern. I just ground out the stamped part and this put me just over 80% of the cylinder exhaust port size. Then I crimped it back together.

 

Im liking it !

 

What kind of improvement are you noticing on the 7910's with just the muffler fix?
Also, can you get your hands on the tool for tuning the high side of the carb?

 

Aside from heat, what are your secrets/ tools of choice for the uncrimp & crimp on the muffler halves?

 

I MM’d my 7910 in December. At first I used propane to heat it and found that a normal pencil flame torch wasn't getting it hot enough so I picked up one of those “spiral” torches, and it made a HUGE difference in how quickly and hot I could get the crimps. Once things were glowing orange, I used a small, round pointed chisel to open up one corner of the crimp. After that I used a cheap screwdriver to pry open the crimp for about 1/2", and then channel locks to bend it all the way open. Then I'd go back to the screwdriver to pry open the next 1/2" and repeat. I had to reapply heat after each step, and I probably wasted a lot of heat putting down a the torch and picking up the screwdriver, so having an extra hand would have sped things up a lot.

 

I also used the channel locks to re-crimp it back together. I did it in two passes, the first time I just closed the crimp back as best as I could around the entire muffler, then I came back a second time and used 2 hands on the channel locks to get it good and tight.

Here's a pic of where I started uncrimping the muffler, on mine this was the easiest access point.

 

I took a pair of 9" side cutters to crimp back. I did uncrimp around the top bolt hole to start.

 

I have not ran it yet but I will let you know when I start the build thread. And yes I can. I think I'm going to order a new one then try to make of fee of them. They should just be round tool with a slot in it by the looks of the carb.

 

Agreed with bassjam. I use a vice, a acetylene torch, a crappy straight screw driver, a pair of crappy pliers. Cause you do get them hot. And will ruin a good pair.

 

Well, I've got a 7910 here that I can't tune, cause none of the tools I have will fit it.
So if ya make an extra and want to sell it, holler. I don't want to go hacking on this one if I don't have to.

 

What's this goofy screw look like?

 

Is it the D shaped one? Nate vansickle has them.

 

I'll have to get a pic of it... Nothin I tried fit..

 

Dremel a slot in it?

 

Can't get muh needle nose pliers in there to get it out.. It's shrouded... Maybe a half used cutting wheel would work, but I'd rather just have the tool.
It's too fat, or I'd put it a little higher on the priority list...

 

I'll ask Nate if he has the tools for sale.

 

Double D. They have them on ebay. I couldn't find them threw my supplier so I had to email them this was my response. It will crack you all up.

 

Wow they are getting more aggressive.

Wittle down one of those Harbor Freight oscillating tool bits so it will fit. damm EPA saving the world one fried 2-stroke at a time.

 

Let me see if I can order you this tomorrow. 234. No part number so well see.