Author Topic: CS-400 Muffler Mod  (Read 4374 times)

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Offline huichex

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CS-400 Muffler Mod
« on: December 06, 2013, 02:21:35 pm »
Hello all, I am new here, and to chainsaws. I was going to post in the current thread, but the site suggested that I start my own thread due to how long it had been since anyone had posted on it.

I am very interested in muffler modding my new CS-400. I was wondering if anyone had pix of the process, or a good description of what to do. I got as far as needing to split the muffler and remove everything. I was wondering if I needed to open up the inlet or the outlet as well. I figure that once I do this I will take it to a shop and let the tune the carb. so someone with a bit more clue that I can do it right.

Secondly is there anything that I could do to the intake that would help wake this saw up?

I would appreciate any help that I can get on doing this work, and look forward to the advice.



Thanks in advance.
Luis

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Offline Moparmyway

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Re: CS-400 Muffler Mod
« Reply #1 on: December 06, 2013, 09:00:13 pm »
I would tune it myself ..... its easy
Just do the muffler mod and then back out the high speed screw about 1/2 of a turn and start cutting some wood slightly larger than your bar. Make sure your chain is sharp. You should hear a crisp sounding 2 cycle while "in the cut" and keeping WOT while you lift out of the cut, it should warble and 4 stroke. Look for max chain speed while in the cut as you slowly turn the high speed screw. You may need to go slightly leaner than the 1/2 turn out - but it should be close. Double check yourself by lifting the saw out from the cut, with WOT so you hear that 4 cycle warbling.

You should notice more power right away. I tune my saws while in the cut for max power, or max chainspeed while cutting (same thing) and when out of the cut mine 4 strokes heavily. I turn the screw as she is cutting and try for a slight 4 stroke warble while she self feeds in the cut (no pressing down on the handle, just holding WOT and allowing the chain to pull itself down into uncut wood)

https://www.youtube.com/watch?v=LImYkWMM21U


Offline huichex

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Re: CS-400 Muffler Mod
« Reply #2 on: December 06, 2013, 09:32:30 pm »
Thanks for the quick response, and the good input. I want to apologize for the nub questions and please correct me if I'm wrong. I assume that backing the high screw out will richen the mixture.  (This seems like a dumb question I just want to be sure im clear as to what im doing) can you read spark plugs for mixture like you can on a 4 stroke?

Also what do I do to the muffler other than gut it out and use the same exit deflector? Or do I need to open the inlet and put a piece of pipe in there?
Thanks again
Luis

Offline 660magnum

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Re: CS-400 Muffler Mod
« Reply #3 on: December 06, 2013, 09:43:00 pm »
Gut the muffler and make the outlet larger is the intent of a muffler mod.
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
Be all that you can be . . .

Offline Moparmyway

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Re: CS-400 Muffler Mod
« Reply #4 on: December 06, 2013, 10:03:10 pm »
Reading plugs is just a good start, if you know what you are doing. Plug deposition will change from WOT to idle. Whats to say that you arent looking at a plug that was blackened by a rich low speed setting, while running lean on the high end ?

Tune it in the wood and start with it rich. Ears are way better than eyes to tune with on 2 strokes IMHO. This way you know you must lean her out a little and you wont do any damage while running @ WOT.

Offline huichex

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Re: CS-400 Muffler Mod
« Reply #5 on: December 07, 2013, 06:16:57 am »
Thanks again for the reply guys. I think sounds like me doing the tune is probably not out of the question, sounds like its straight forward. I will try and look at the saw in the next few days, and locate the high screw on the carb.

@660 I guess I wasn't clear enough on the question about the actual mod on the muffler. I am asking to make sure that I don't cut to much or not enough. I get that the point is to free up the exhaust to allow the motor to breath more and thus make more power, but surely there is a point where the there hole either on the inlet or the outlet of the muffler are too big, and then you are either losing power or the lack of backpressure makes the motor untuneable. That's why I was hoping to see some pix of what guys are doing to them that works.

Based on the pictures that I have seen of the outside of the mufflers, they are putting pipes as outlets and what not, didn't know how far into the muffler case those pipes went, or where to buy pipes that small and thin. I have access to a welder and  I plan to post pix of what I end up doing, just want to do it nice and right.

@Mopar Thanks for all the good info. The saw in the vid sounds killer, its vids like that that make me want to do this to my own saw.
Thanks again to everyone in advance.

Offline farmboy

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Re: CS-400 Muffler Mod
« Reply #6 on: December 07, 2013, 07:39:32 am »
Rule of thumb is 85% of the ex port no spark screen or same size as ex port with spark screen.  The CS400 comes alive with a MM.  Neighbor was looking @ a Stihl MS290 I have for sale, as he said he needed a bigger saw.  I MM'd his CS400 and it cost me the sale.
Shep

Offline Moparmyway

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Re: CS-400 Muffler Mod
« Reply #7 on: December 07, 2013, 08:23:44 am »
On that 330EVL, I made the hole as large as possible and still kept the plastic cover, without hogging that out.
On some of my other saws, the hole in the muffler is even larger than the hole at the cylinder. On the AS forum there are many threads showing gains due to increasing muffler outlet up to 175% (of exhaust opening @ cylinder exit). Dudes were noticing idling problems with a hole too large (IIRC, over 180%), but even @ 150% saws idled fine and produced more power than when the hole was 125%.

The larger the hole, the louder the saw. Hole placement also plays a role in saw loudness

On the pics of the 330 EVL, first one is stock, second is MM'd

On the 044, the first one is a stock opening, second one is a MM'd opening (2 different saws)

Offline mountainlake

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Re: CS-400 Muffler Mod
« Reply #8 on: December 07, 2013, 09:08:20 am »
Rule of thumb is 85% of the ex port no spark screen or same size as ex port with spark screen.  The CS400 comes alive with a MM.  Neighbor was looking @ a Stihl MS290 I have for sale, as he said he needed a bigger saw.  I MM'd his CS400 and it cost me the sale.
Shep

 A good muff modded CS400 is real close to a Stihl MS290 in cut times and 3 1/2# lighter ready to cut, no way would I run a MS290.  Steve

Offline huichex

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Re: CS-400 Muffler Mod
« Reply #9 on: December 07, 2013, 09:53:47 am »
Awesome! Now we are covering ground on the mm portion of this project. Should I do anything to the muffler inlet at the head?
Thanks again guys!

 

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