Dolmar 64xx/73xx/79xx series, smurfs and solo 665/675/681 thread

[RI Chevy]

Nice Wilhelm

 

[huskyboy]

Meant to post this a while back but this is how I open the 7900 muffler without heat.

 

[Wilhelm]

I did three of mine with a side cutter, once One gets the hang of it it is quite simple.
All of mine are regular steel mufflers, NOT stainless steel!

 

[huskyboy]

I did three of mine with a side cutter, once One gets the hang of it it is quite simple.
All of mine are regular steel mufflers, NOT stainless steel!

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Yup side cutters work well too

 

[huskyboy]

I cut the bird cage off of the back plate and reinstall it. It has alignment pins holding in place and gets sandwiched in place when muffler is crimped back together. No need to weld it or braze it. Not sure about the 7910/6421 style muffler. They might be a different story.

 

[Wilhelm]

On the SLR mufflers the tubes "plate" also doubles as a spacer and should be reused.
No need to weld or braze it on either, it is sandwiched between the bolt tubes and the mufflers back half.

 

[huskyboy]

On the SLR mufflers the tubes "plate" also doubles as a spacer and should be reused.
No need to weld or braze it on either, it is sandwiched between the bolt tubes and the mufflers back half.

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Thanks wilhelm

 

[mettee]

I cut the bird cage off of the back plate and reinstall it. It has alignment pins holding in place and gets sandwiched in place when muffler is crimped back together. No need to weld it or braze it. Not sure about the 7910/6421 style muffler. They might be a different story.

I think the reason it gets welded back in for some, is that when you remove the internals you remove supporting material, the muffler then puts a lot of force in the one place its connected and it can crack. Lots of harmonic coming off the cylinder. The mufflers you guys have don't have the front brace dolmar added on the newer saws.

 

[Mastermind]

I braze em in because I port match the back half to the jug before I crimp it back together.

 

[mettee]

The two inserts that are there twist off easy, so I am tacking those in. The two tubes where the screws go in, get wallered out like you see, so that's why I want to weld in part of the cage for support. I'm still up in the air on removing it completely.

 

[huskyboy]

I braze em in because I port match the back half to the jug before I crimp it back together.

Aha that makes sense now. Those alignment tabs would be ground off in the process port matching to the ported cylinder.

 

[Mastermind]

Aha that makes sense now. Those alignment tabs would be ground off in the process port matching to the ported cylinder.

On the 7910.....the difference is huge too.

 

[huskyboy]

On the 7910.....the difference is huge too.

View attachment 145640

That’s right, I forgot about that ridge that has to be ground in exhaust

 

[huskyboy]

So if it’s a stock cylinder one could get away without brazing or welding it in, and if it’s ported definitely weld/braze is the consensus? I’m really liking how this thread is coming along. Lot of good info here.

 

[Mastermind]

So if it’s a stock cylinder one could get away without brazing or welding it in, and if it’s ported definitely weld/braze?

That's a stainless muffler, and if I remember correctly, the flange is spot welded to the shell from the factory in those. But.....if you're doing a 6400/7910 conversion with a galvanized muffler, you would definitely wanna braze in the flange.

 

[huskyboy]

That's a stainless muffler, and if I remember correctly, the flange is spot welded to the shell from the factory in those. But.....if you're doing a 6400/7910 conversion with a galvanized muffler, you would definitely wanna braze in the flange.

Thanks Randy

 

[huskyboy]

Found one of my pictures from when I gutted it. I can definitely see how if it was ported those holding tabs would get ground off especially with 7910 cylinder. That red top 7900 is staying stock porting wise so I’ll leave it. This 6421 here the muffler looks completely different. Haven’t attacked it yet...

 

[Mastermind]

Thanks Randy

You're welcome Mason. Now......GTG my place, second weekend of Oct.

Gonna do a 7900 build off. Be there.

 

[huskyboy]

You're welcome Mason. Now......GTG my place, second weekend of Oct.

Gonna do a 7900 build off. Be there.

You got it, I found a 7900 carcass from Dustin to hopefully clean up that cylinder to put in the 6421. Might have Doc help me with the porting since he is close by.

 

[Mastermind]

You got it, I found a 7900 carcass from Dustin to hopefully clean up that cylinder to put in the 6421. Might have Doc help me with the porting since he is close by.

Bring your dad. I like him.....