Cs-590/620 muffler mod

[STOVE]

I have read a lot on the site about the different ways everyone modifies the cs590/620 muffler. As well as the bold on aluminum port for the top.

Being a one piece design it doesn’t allow for a bark box style.

Has anyone added a universal style port to the side of the muffler? Is it possible with no access to add a nut ? Would be a weld up I assume or a pop rivet .

Would that addition even be worth it?

 

[NSEric]

You can just cut a fish gill in the side of the muffler in front of the seam and pry it open, no need to weld.
A lot of guys totally gut the muffler under the stock deflector, it makes them run good but is very loud as the baffles in the middle of the muffler make it act like a tiny little can with the opening back there.
IMO it's better to have an extra opening in front of the baffle plate/crimped seam on these saws instead of a big opening behind the baffle plate.
I have both on my saw, I didnt open it up too much under the deflector and it wasnt too loud or very fast so I added the fish gill and it liked that and runs better.

 

[Johnwell]

I have a 590 that I bought used that somebody gutted the muffler on. It was obscenely loud so I welded a 3/4” pipe back in the muffler and made a plate with a ~1/2” hole through it to tame it back down. Still flows better than stock, but far less obnoxious.

 

[WoodmanSr]

Has anyone added a universal style port to the side of the muffler? Is it possible with no access to add a nut ? Would be a weld up I assume or a pop rivet .

Not used then but kits from Westcoastsaw.com offer that solution. A bit pricy but nice stainless deflectors, 3 sizes choice, or hardware kit only for $7.95.

HW kit comes with a nut (piece) to crush & crimp the blind nut inserts to your muffler shell.

Search their site;

UNIVERSAL POWER PORT​

 

[STOVE]

Not used then but kits from Westcoastsaw.com offer that solution. A bit pricy but nice stainless deflectors, 3 sizes choice, or hardware kit only for $7.95.

HW kit comes with a nut (piece) to crush & crimp the blind nut inserts to your muffler shell.

Search their site;

UNIVERSAL POWER PORT​

Egan has a port as well, but I’m really wondering if adding one on the side would add any performance

 

[Chevboy0167]

The real benefit is heat reduction. More air volume through a hot tin can reduces temperature.... also pulls heat away from cylinder like a heatsink.

Cooler saw is a happy saw......

 

[STOVE]

The real benefit is heat reduction. More air volume through a hot tin can reduces temperature.... also pulls heat away from cylinder like a heatsink.

Cooler saw is a happy saw......

Is there a point of diminishing return? Watching some of the Dyno joe 026 videos he mentioned some power loss with too much air flow?

 

[RedneckChainsawRepair]

If you got 30mins this is totally free.

Pull that inner and cut off top part to use as a metal gasket for the top deflector if want to. Hole behind tube all that is needed or go in and remove the whole tube and open right there.

Be sure to pull stops to retune carb and enjoy better running saw.

 

[Marley5]

Is there a point of diminishing return? Watching some of the Dyno joe 026 videos he mentioned some power loss with too much air flow?

I believe so.
I never mess with the port side and only open up the exhaust 80% of the port.
Like mentioned you'll have to remove the limiters and Re-tune saw.
Once this is accomplished, you'll have a much better running saw.

 

[STOVE]

I believe so.
I never mess with the port side and only open up the exhaust 80% of the port.
Like mentioned you'll have to remove the limiters and Re-tune saw.
Once this is accomplished, you'll have a much better running saw.

I am buying it used from a member here. He has done some muffler work to it already. I will certainly tune as hen says it has not been done yet.

I have only seen one photo in all my googling and forum searches with a side port added

 

[STOVE]

If you got 30mins this is totally free.

Pull that inner and cut off top part to use as a metal gasket for the top deflector if want to. Hole behind tube all that is needed or go in and remove the whole tube and open right there.

Be sure to pull stops to retune carb and enjoy better running saw.

I assume the noise level on that style is quite loud.

 

[Breckinridge Elkins]

I bought mine used and the PO had already opened up the port with a dremel. I cleaned up his cuts and added the spark screen back. I can't see spending the bucks on those big milled aluminum deflectors, though they do look pretty cool. If you wanted to truly gut the muffler, you can heat the seams with MAPP gas and separate the halves.

Is there a point of diminishing return? Watching some of the Dyno joe 026 videos he mentioned some power loss with too much air flow?

That's what I always thought but I have read differently on this site. Small 2-stroke engines don't benefit from exhaust backpressure the way some other engines do. As for the power dropping off a little after a muffler mod, it's likely because it needs to be retuned.

 

[Johnwell]

…That's what I always thought but I have read differently on this site. Small 2-stroke engines don't benefit from exhaust backpressure the way some other engines do. As for the power dropping off a little after a muffler mod, it's likely because it needs to be retuned.

The only way a muffler modded chainsaw would be making less power after a retune would be if you ended up outside of where your stock carb could adjust. Which can happen.

 

[STOVE]

The only way a muffler modded chainsaw would be making less power after a retune would be if you ended up outside of where your stock carb could adjust. Which can happen.

From what I understand the echo high jet has to be swapped to prevent an autocorrection of a too lean scenario

 

[Breckinridge Elkins]

The only way a muffler modded chainsaw would be making less power after a retune would be if you ended up outside of where your stock carb could adjust. Which can happen.

My point being, opening up the exhaust flow will require a retune.

From what I understand the echo high jet has to be swapped to prevent an autocorrection of a too lean scenario

Wouldn't you just...turn out the H screw a little?

 

[NSEric]

My point being, opening up the exhaust flow will require a retune.

Wouldn't you just...turn out the H screw a little?

Echo puts a governed high jet in the 590 and 620 carbs, it's why they're kinda slow stock, it kicks in at about 12000rpm.
You can turn the high screw almost all the way in and it's still too rich after you mod the saw. It's weird, when you open the muffler up it pulls more through the govern jet and you need to lean the screw out to get it to stop four stroking.
You can swap the jet to a normal non governed jet or block the hole in it with jb weld. After this it will adjust like a normal carb but is closer to 2 turns out not 1 turn out on both screws.

 

[Breckinridge Elkins]

Echo puts a governed high jet in the 590 and 620 carbs, it's why they're kinda slow stock, it kicks in at about 12000rpm.
You can turn the high screw almost all the way in and it's still too rich after you mod the saw. It's weird, when you open the muffler up it pulls more through the govern jet and you need to lean the screw out to get it to stop four stroking.
You can swap the jet to a normal non governed jet or block the hole in it with jb weld. After this it will adjust like a normal carb but is closer to 2 turns out not 1 turn out on both screws.

I've never heard that. Do you have a P/N?

 

[Marley5]

These muffler mods are great topics, love hearing everyone's experiences.
The last muf mod I did, it leaned out on the low jett and would lose idle after about 30 seconds.
I don't touch the H until I'm in wood.

 

[Woodtroll]

Echo puts a governed high jet in the 590 and 620 carbs, it's why they're kinda slow stock, it kicks in at about 12000rpm.
You can turn the high screw almost all the way in and it's still too rich after you mod the saw. It's weird, when you open the muffler up it pulls more through the govern jet and you need to lean the screw out to get it to stop four stroking.
You can swap the jet to a normal non governed jet or block the hole in it with jb weld. After this it will adjust like a normal carb but is closer to 2 turns out not 1 turn out on both screws.

I opened up my muffler just slightly by removing the screw-on exhaust guide from the top of the muffler, and cutting a square out of the lower sheet metal plate so the exhaust comes straight out of the muffler up against the top guide then out. In other words, you can now see a lot more of the spark arrester screen than before. I didn't drill any holes in the inside of the muffler below the arrester screen.

I had previously removed the adjustment limiters and had the saw running well, with a nice neutral tan plug color. Once I did the muffler mod, I wasn't able to get the saw to lean out of four-stroking on the high side; even with the screw lightly bottomed out the saw is running too rich with a dark arrester screen. I thought I had read somewhere that the saw would need to be richened up on the high side after the muffler mod, but I guess I remembered wrong?

I think the correct nozzle without the hole is Walbro #86-578-1; can anyone confirm this, please?

I hope this goes along with the thread content without being considered a hijack. I apologize if this is too far out of line.

 

[STOVE]

I opened up my muffler just slightly by removing the screw-on exhaust guide from the top of the muffler, and cutting a square out of the lower sheet metal plate so the exhaust comes straight out of the muffler up against the top guide then out. In other words, you can now see a lot more of the spark arrester screen than before. I didn't drill any holes in the inside of the muffler below the arrester screen.

I had previously removed the adjustment limiters and had the saw running well, with a nice neutral tan plug color. Once I did the muffler mod, I wasn't able to get the saw to lean out of four-stroking on the high side; even with the screw lightly bottomed out the saw is running too rich with a dark arrester screen. I thought I had read somewhere that the saw would need to be richened up on the high side after the muffler mod, but I guess I remembered wrong?

I think the correct nozzle without the hole is Walbro #86-578-1; can anyone confirm this, please?

I hope this goes along with the thread content without being considered a hijack. I apologize if this is too far out of line.

I want to know the part number as well.