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 Chainsaw help.... 
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My neighbor said I could use his chainsaw.... IF I could get it running.... I took that as a challenge!

So - its an Echo CS310 - less than two years old.....
It starts and idles, but bogs and dies when you pull the trigger. You can 'finger' the trigger to get it to rev up, but once you hold it, it just dies....

This is what I have done so far ---
- Pulled the carb - checked the diaphragms - all 'looks' ok (Walbro wt 835 carb)
- Cleaned the metering valve since it had some build up (not much)
- Pulled the spark arrestor screen (this was my bet after the carb looked good) - no build up at all
- Pulled muffler - no exhaust port build up - piston looked pristine
- Pulled the gas tank vent valve - seems to be venting properly
- Checked gas filter - not plugged
- Gas lines look ok without any cracking (its less than 2 years old)
- And YES - new gas

I'm at a loss at the moment as to what it could be. My gut says to get a carb rebuild kit just in case it is the metering pump diaphram, but I don't have any confidence that is the problem. I'm hesitant to pull the metering screws since they have the 'don't fuck with it' caps, and I don't want to try and tune it afterwards - but it could be just a bit of crap on the high screw tip.

I've seen on a forum that there have been instances of the rubber boot between the carb and the cylinder will crack or tear, especially after the saw has been 'pinched' and people yank on the unit to get it unstuck --- I haven't figured out how to inspect that yet without tearing the whole thing down....

What else should I be looking at? The saw isn't that old and hasn't seen much use, so I'm assuming it HAS to be something simple....

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Plan B is actually repeating Plan A.... it just involves much more alcohol.

Of the ten voices I hear in my head, only three keep telling me NOT to shoot....
Do I go with the majority or common sense?


Thu Feb 27, 2020 10:52 am
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you didn't mention the spark plug

also did you check the choke?

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Thu Feb 27, 2020 10:58 am
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I realized as I was typing that I have not checked the plug yet, but I will today.... I'm betting that its okay.
The choke appears to be operating correctly - its the kind that 'sets' when pulled and is deactivated when you pull the trigger. The saw will die if set again while idling... The interesting thing is that when you start it up with the choke, it locks the throttle at ~1/2-2/3 throttle and it will rev there - as soon as you pull the trigger, the choke is deactivated and any trigger action past ~1/2 will kill it.

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Plan B is actually repeating Plan A.... it just involves much more alcohol.

Of the ten voices I hear in my head, only three keep telling me NOT to shoot....
Do I go with the majority or common sense?


Thu Feb 27, 2020 11:06 am
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I've heard hearsay that cracked impulse lines are a problem on echos.

Other than that, tweak the fuel screw for high speed... Maybe it's running too lean?


Thu Feb 27, 2020 11:43 am
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The carb internals are most likely varnished....very common problem with small carbs. I've repaired several in the past by running some acetone through them to clean them out. Good luck!

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Thu Feb 27, 2020 11:45 am
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Yeah - I've already played with the mixture screws - within their 1/2 turn limiting caps - without any improvement... It still just bogs out and dies. It just doesn't seem to have any power once you get past ~1/4 throttle.

_________________
Plan B is actually repeating Plan A.... it just involves much more alcohol.

Of the ten voices I hear in my head, only three keep telling me NOT to shoot....
Do I go with the majority or common sense?


Thu Feb 27, 2020 11:48 am
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Lew wrote:
The carb internals are most likely varnished....very common problem with small carbs. I've repaired several in the past by running some acetone through them to clean them out. Good luck!


I taught my kids at an early age to pull float bowls and sniff their fingers for signs of varnished gasoline.

Probably die early from some kind of finger or nose cancer, but they are pretty handy around the house. Hahaha

Old gas goes down the toilet nicely, but I usually have a fire extinguisher and a glass of bourbon handy.

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Thu Feb 27, 2020 11:52 am
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Get rid of the limiters.

Fatten up the high speed until it blubbers at full throttle. Then keep fattening it up until it dies.
If it wont richen up enough to kill you may have an air leak. If it can be richened up enough t okill it then you most likely dont have a cracked boot or bad case seals.
If it has a cracked boot it will pull more air than you can tune out by adding more fuel/fatten.

Any saw/small 2 stroke with limiters is usually WAY to lean. They do this so they will pass EPA.

Here at sea level we have lots of oxygen and the saw needs LOTS of fuel.

What are you running for saw oil/mix? Ratio?

God oil, preferably Stihl oil STRICTLY at 50/1. NEVER more oil.


Thu Feb 27, 2020 2:21 pm
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Did ya clean the air filter?


Thu Feb 27, 2020 2:28 pm
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^^^^^
What he said. At a minimum, clean & gap the spark plug. If it's of an unknown age, toss it & put in a good replacement.

Do you run gas with alcohol in it? I've found that to be very problematic and refuse to run it in any of my small engines any longer. 95% of my small engine problems went away (chainsaws, outboards, generator, etc.) after I did. I can usually start my generator with 1-2 pulls after a year of sitting, same with my 10 hp outboard on my boat. When I was using alcohol based gas that wasn't the case.

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Thu Feb 27, 2020 2:29 pm
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Didn't see it mentioned, but some saws have a weighted filter in the fuel tank on the fuel pick up line. If it gets clogged/gummed up the saw will idle OK, but starve out when you gun it. Worth a peek.

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Thu Feb 27, 2020 6:36 pm
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So.... I pulled the carb again today and gave it a good spray down with carb cleaner even tho there didn't appear to be any varnish - it looked perfectly clean. Check the gap on the plug - looks good. I did look at the fuel filter earlier and it looked fine - basically new compared to the 20 year old one in my weed whacker, but I'll pull it tomorrow and try again to verify thats not the problem.

No impulse line - just the standard hole on the carb housing - cleaned it out too. Same results with or w/o the air filter.

I did have a left over 'pump' gasket - the one with the flapper valves for the bidirectional pump circuit (whatever its called) - and replaced the one in there because the flappers/valves looked a bit limp, but that didn't seem to improve anything. The metering valve diaphram 'looks' good, but being that it won't rev, I'm thinking that may be the problem. Its either that or an air leak that I haven't seen yet.

I talked to the owner tonight to see how much he wants me to do - I don't want to fucker it anymore than it is. He's gonna look into return or warranty before I go any further -- scrapping the limit caps and screwing with the H/L screws too much. If he can't get any results from return or warranty then I'm gonna say carb kit and play with the mix screws until it works.

I did think I fuckered it up tonight --- 7th time taking the carb off - undo throttle linkage.... and it falls off! Trying to figure out how to reattach to the trigger ?!?!?! No holes - can't find where the bends go ----- CRAP! Couple of youtube vids made it look too easy... FUCK ME - that throttle wire/bar just floats on the trigger... being held in place by a friction fit in a guide in the handle... I expected a more positive lock.

And even on the 7th time reassembling, I still managed to forget to check the hose routing before assembly and pinched the hose yet again.... dammit.

_________________
Plan B is actually repeating Plan A.... it just involves much more alcohol.

Of the ten voices I hear in my head, only three keep telling me NOT to shoot....
Do I go with the majority or common sense?


Thu Feb 27, 2020 9:57 pm
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I was thinking about this last night, and I remembered a problem I'd run into with a 5hp outboard a while back. It just would not run properly, where it used to run just fine. I found the exploded parts diagram and noticed I was missing a little rubber cup shaped like a tiny thimble that sat on top of one of the jet towers (fast?) by comparing the diagram to the actual carburetor. Once I ordered a new thimble(?) and installed it, it started running like a top again. No idea how I lost it, for all I know, it's still sitting in the gravel in my backyard where I was working on it last. Not saying that's what wrong with yours but might be worth the time to do the comparison to make sure all the pieces-parts are there and accounted for.

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Fri Feb 28, 2020 10:29 am
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A CS320 isnt that old of a saw. I doubt its a cracked boot or line. Its something simple.

MOST LIKELY A TUNE.

Between me and my firewood guy, we have 4 Echo saws. ALL run great weekly/daily ON ethanol fuel from AMPM. NONE have ever needed a carb kit or fuel line. 2 of them I got for $50 each (50/55cc) and one of the firewood guys echos (55cc) he got for free.

Clean and properly tuned. Makes a saw happy. Many people think into these things way to much.


Fri Feb 28, 2020 12:33 pm
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I'm willing to pull the limit caps and tune.... but I just don't understand how the saw could get so far out of tune in 1 1/2 years?? More than the 1/2 turn limits on the cap?

Gonna wait and see what the owner wants to do --- I don't want to make any 'obvious' signs that it has been molested (such as removing the limit caps or buggering them up) if he can return or get warranty repair first.

I will note that the carb did look exceptionally clean to begin with --- the only sign of concern I noticed was a small amount of whitish build up on the metering diaphragm - didn't look all that bad, and the diaphram still moved nicely.

_________________
Plan B is actually repeating Plan A.... it just involves much more alcohol.

Of the ten voices I hear in my head, only three keep telling me NOT to shoot....
Do I go with the majority or common sense?


Fri Feb 28, 2020 1:00 pm
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