Dolmar 6400 Muffler Mod.

I've never done more than routine maintenance on my saws so I'm going to need a little direction on what all I need to do with this mod. What I have is a new to me Dolmar 6400 that I picked up on C/L. I believe is a 2011 model. Runs good but the muffler gets so hot that it is making the plastic cover smoke. I'm not sure if it has a Kat or not but I'm going to gut the muffler to see what's inside. My questions are do I remove all of the baffles inside? Do I need to Retune to carb when I'm done? I will post pictures when I get started this week end. Thanks for any help in advance.

 

Hopefully they'll check this out. I like the saw but would like it to run cooler.

 

Don't know if it's relevant or not, but I recently drilled a 5/16 hole straight through the Cat on my trimmer and it made a ton of difference in running temperature. You will for sure need to readjust the carb if you mod the muffler for increased flow. It may be on the lean side now if it's getting that hot.

Edit: Nice Truck! Marty McFly would surely approve!

 

Is it a cat muffler? You can heat the crimp up and open the muffler and pull the cat out. Add another outlet and gut the cage if you so wish while it's apart. Then add an extra outlet and put it back together.

 

I would drill a drill a hole through it but I can not see it through the opening on the muffler. (I got the truck from Marty back in 88 thanks)

Thanks for the advice. I was just going to cut it open and weld it back together but if I can heat up the crimp then I'll try that first.

 

^ says it well. Tippy will have to retune it. also take the muffler off the saw for any cutting , drilling or grinding. Also rinse very thoroughly to make sure all metal shavings are out of the muffler
.

 

Also will add that total exhaust holes should not go over 80% of the exhaust hole size on the cylinder.

 

I have the muffler off of the saw. To be no bigger than it is it is heavy. Thanks for letting me know to rinse it. I'm not sure if I would have though of that. Who it Tippy?

 

I"m not sure if I'm going to open up the port any bigger or not. I'll keep that 80% in mind if I do.

 

I go a lot more than 80% on stock saws. 100% if you use screen. 140% or more on ported ones.

 

Where did this 80% come from? I have heard this before and this seems to be the number people aim for. I have exceeded 80% a few times with good results tho.

 

I removed all the material under the deflector on my 6421 with a dremel. Since the muffler was already split it was very easy to do. I didn't feel like it was a big gain but it made me feel better when the cat was out. I'm not sure your 2011 model has a cat tho.

 

6400 muffler, opened up as per mdavlee instructed, middle sandwich plate with CAT mounted was tossed, diffuser drilled out, the port was matched, stock outer port enlarged, and the extra outlet was fabricated



You WILL need to re-tune as others have already discussed

 

80% is something for the idle quality and flow once the exhaust is cooled some. If you use restricted screen then go 100% if you want to use that rule to stay close. Usually 150-200% will still idle pretty good on a saw.

 

I heated and open the crimp with no problem. Took out the metal Catalyst screen and re-installed without any other mods. Runs much cooler with hardly an increase in noise and very little tuning needed. I buffed the stainless muffler while it was off- might not have improved anything but looked nice for a while hahaha.

 

I did the same but did open the the outlet some, and mine is SO LOUD! I've ran my saw a couple times without ear protection when dropping large trees and it made my ears ring. Looking back I wish I had just taken out the cat like you did.

Of course I gutted the muffler at the same time I was putting the 79cc top end on. So I'm sure both mods contributed to all the extra noise.

 

X Got it a part. When baby girl takes a nap I'll weld it back together. I really appreciate all of the information y'all have gave me. I'll post some more pics after I'm done welding.

 

and that is the reason i stick to just removing the bird cage and 2 inner plates, leave the outlet alone on a 6400 muffler no matter whether it is a 6400 or 7900 cylinder on it. keeps the noise level to something tolerable.

 

Got it back together.