Chainsaw carb tweaking and temperature

skier219September 19, 2011

I have been working with a new Echo (CS-400) saw since Hurricane Irene mowed through the area, and have probably cut down or cleaned up over 25 trees in the last 3 weeks. The saw has been working great, and I am near the point where I will run it dry and put it into storage for the next emergency.

The Echo manual suggests doing carb adjustment after the saw has broken in (they say after two tanks of gas, and I am well past that point). But the saw runs excellent over the whole speed range once it's warmed up, and I am hesitant to fiddle with the carb at all. Does it make sense to just leave it alone? Without a tach, I doubt I can tune it any better by ear than it's already running.

I did rebuild the carb on a 40 year old Poulan (S25DA) recently and got that running in tip top shape, which was fun. The saw is practically a family heirloom, having cleared land and heated homes over two generations so far.



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Skier: Normally a tach is only required when you have done extensive saw modification . I usually use only if muffler modifications or porting has been done. I would just fine tune the high speed , if the low speed performance does not have any lag or hesitation . Turn the high speed jet in until Max RPM is achieved then turn out until it diesels then in until it cleans out . Ensure the tuning is done with at least a 3/4 full fuel tank , clean air filter and fuel filter new or very clean spark plug and a warmed up saw , this will ensure a long term tune up . As for storage ensure you put in some fuel treatment prior to running all the fuel out .

Note: Your Poulan was a very stout 38 cc. unit in its time . Built on a very Reliable Magneisuim Chassis . Acutally one of the last good saws Poulan put out before they were bought out and became a disposible chainsaw manufacturer . Happy Cutting .

    Bookmark   September 19, 2011 at 3:32PM
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ewalk, thanks for the info -- glad to hear your procedure for adjusting the high speed jet. By the way, I do notice some slight hesitation throttling up from idle when the saw is cold, but it's gone once the saw has warmed up, so I assume it's not a big deal. If that did occur on a warm saw, I would want to back out the low speed screw a bit, correct?

What kind of fuel treatment do you suggest?

The Poulan is quite a saw. They don't make them like that anymore -- I really like the magnesium frame and case. It's a pity Poulan has turned into a nametag for cheap plastic saws.

    Bookmark   September 19, 2011 at 8:09PM
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I hope this is not Jumping Your Post! I have heard negatives about Poulan but the old S25 has been Super. They are the only saws I have purchased Mid 70 and mid 80s. They are durable and will rebuild for my avg 2-4 + cords of cutting per season.

1. My original lasted 10 + seasons before a wrist pin keeper failed and ruined the cyl and another purchase was my best option.

2. The 2nd saw locked on a 100 + TX degree day (mix or heat was my opinion) but only a new piston and rings vs cyl has given me over 10 years on that job (vs wanting the next grade of saws I am seeing).

3. When the 1st saw went down, I purchased a used S25 grade as an interim until I could purchase the next new S25. These 3 saws have been all I could expect vs what I am seeing on the market today.


    Bookmark   September 19, 2011 at 9:39PM
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Feel free to jump in to talk about the S25! What amazes me about my saw, which was built in 1972, is the tough life it led before it came to me.

My father borrowed it from a neighbor to clear the lot for his first house in 1972 or so. The neighbor had bought it to clear their lot a few months earlier. Later, my father bought the saw from them. It did firewood duty for a few years after that, then cleared another lot. More firewood for 15 years, then cleared their last lot (my parents liked building houses). From there, it was mainly used for yard chores and storm cleanup before coming to me in 2002 or so, just in time for Hurricane Isabel.

It's amazing to me that a top handle saw with a 14" blade did so much grunt work, including clearing all those lots. It's definitely not the saw I would choose for heavy felling and bucking, but that didn't stop my dad. In fact, he ended up being the go-to saw guy that friends, neighbors, and relatives called when they had a tree problem. The S25 did it all.

I mainly used the S25 for yard chores. I pulled it out the Friday before Hurricane Irene came through, to cut down two 24' Leland Cypresses that had gotten too tall next to my house, and to cut out a few limbs hanging over my shed. After many years of inactivity, the saw started fine, but was very temperamental when I was stopping and starting (ended up having to leave it running). That prompted me to pick up the Echo after the storm, since I suddenly had a much bigger workload to deal with.

Later, I went back and took the S25 apart, giving it a thorough cleaning (pretty sure the saw dust/oil sludge accumulated inside the case was decades old). Anyway, I found that the tip of the carb inlet needle was broken off, which explained occasional flooding. And the plug wire had a huge gash and was likely shorting against the fins on the underside of the engine from time to time. I sealed and taped the cable (routing it a bit differently this time), installed a new fuel line with filter, rebuilt the carb, and also filed and trued up the bar.

Now the saw starts easily, and runs great. It doesn't cut nearly as good as the Echo, but that's to be expected. Still, for a ~40 year old saw, it's pretty impressive to me.

At some point, I want to replace the S25's drive sprocket, since it's a bit chewed up. Oddly, the sprocket is a 9-tooth design driving a 1/4" pitch chain. I don't think that's original, but am not 100% sure. Rather than spend the money on those more obscure parts, I think I will probably upgrade to a new bar and go 3/8" for the chain and sprocket.

    Bookmark   September 19, 2011 at 10:13PM
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The versatile use of the S25 is what sold me on the saw vs cutting many 24" + dia trees. It was light on my back and would get the job done with good maintenance. I used 16" bars originally but went to some 14" and finer teeth for trimming. I have gone through many bars and chains due to cutting wood that had been Dozed in sand. That led to buying new, used and new chain stock surplus and adapting and sharpening. Plus, the laser tip bars vs sprockets are worth the money. Now you know I have a surplus of clutches and kits that will match chains. I let all rest a little more now even though my friends think I'm still on "24/7 Tree Is Down Call"! LOL. loger

    Bookmark   September 19, 2011 at 11:16PM
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Skier : The low jet tuning normally is to richen the mixture so yes turing out an 1/8 to 1/4 turn would be optimium . However with the older saws especially with Tillotson carbs rather than Walbro , sometimes they were a little to rich and would hiccup rather than bog. So try turning the jet out 1st , if the saw runs flat then turn the jet in another 1/4 or so . . As for cleaner I have used Lucas Top end cleaner for yrs but just recently changed to Star*tron at the suggestion of RDaystrom a forum member . I believe that this product is a very good investment within carburation issue prevention . It is available within Walmarts RV/ Marine section. As for your chain the original spec was 3/8 " Semi Chisel , which you can pick up almost anyware. As for Spares parts you can always check out the chainsawr site , since Scott has pretty much anything you will ever need at a very reasonable cost. I currenly have two Pioneers that I have running from time to time for sentimental reasons both are over 53 yrs old (P-20 & 1140 automatic) . Love my Husky and Stihl saws but you just can't believe the torgue the older saws have lol .

    Bookmark   September 20, 2011 at 2:25PM
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Thanks ewalk.

    Bookmark   September 20, 2011 at 10:30PM
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I got the mini version, got it at estate sale basket case. Also got poulan #20 hanging in the back ground. As you can see previous owner ran it without oiler working. But with some help on this forum I got it working. Also got Lombard Little lighting (made in canada) All Mag. cases also. Can't believe I hung my wood shark up with clean up.

    Bookmark   September 22, 2011 at 7:25PM
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Sorry picture didn't post even though is showed on preview.

    Bookmark   September 22, 2011 at 7:28PM
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Rcmoser, What method did you use with sharing Pics? Try a link from your Internet up-load (provider)in your text. That has been my best method when attachments are not a menu option. loger

    Bookmark   September 22, 2011 at 9:06PM
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