Used the wrong 2 stroke oil in ECHO CS-490
- Thread starter Echoman
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- 2 stroke oil cylinder
huskihl
Member
Your piston cylinder look perfect to me, although it’s from a distance. If there are no vertical gray streaks on the piston, it’s probably fine.
I agree with Mr huskihl - piston looks fine as long as the rings are moving freely in the grooves- but there is a fair amount of carbon on top of the piston and in the combustion chamber that could be scraped out whilst you have the opportunity.
Going back to the start and now we have confirmed the piston is not lean melted- have you taken the starter cover off the saw yet?
You say you can pull the saw over but it seems to pull too easily- are you sure the starter pawls, recoil cup or flywheel are not damaged in some way and you are pulling the rope but not rotating the crank?
With the cylinder off can you grab the piston to rotate the crank through 360 degrees and watch the flywheel travel to ensure it follows the same rotation?
Could be a loose flywheel nut and sheared key- pull the rope and the flywheel resistance provided the assumption of the engine turning over- but the crank is not moving enough to compress fuel and fire the saw?
Going back to the start and now we have confirmed the piston is not lean melted- have you taken the starter cover off the saw yet?
You say you can pull the saw over but it seems to pull too easily- are you sure the starter pawls, recoil cup or flywheel are not damaged in some way and you are pulling the rope but not rotating the crank?
With the cylinder off can you grab the piston to rotate the crank through 360 degrees and watch the flywheel travel to ensure it follows the same rotation?
Could be a loose flywheel nut and sheared key- pull the rope and the flywheel resistance provided the assumption of the engine turning over- but the crank is not moving enough to compress fuel and fire the saw?
Hello, I put the saw back together today and started it up again. It seems to be pulling normally. One thing I noticed when I changed out the gas last week was that it must have been some premixed gas since it was pretty clear. When I started it today, I did not have the side cover on so I don't believe the brake would be on in that position, right? the saw just doesn't have the power that it used to have. Maybe replacing the rings would be a good place to start? I just know when that premixed gas was put in is when the problem started. I may just purchase a cylinder and rings and be done with it. I would also think that the new fuel should be in the carb by now.
In my opinion, your original cylinder and piston are in good enough condition to run the saw just fine and replacing them (at some cost) will do nothing to cure your problem.
I will also say I have ZERO experience with canned premix and or ethanol fuel- we just don't have that here where I live. But could it be whatever you are trying to run it on is old, or contaminated fuel that how has a low octane rating?
How long since the saw was shouted a new or at least a thoroughly cleaned air filter? New fuel filter?
Wasted bearings can bind and slow a cranks rotation down- but usually by then they are causing other major problems like cage disintegration and major damage to the cylinder and piston- best way to check those was when the cylinder head was off.
Seized/damaged clutch needle bearing would usually display more as a constant drive to the clutch, or very erratic chain wobble and derailment.
Try stripping the entire clutch side off the saw- no chain, no bar, no clutch and see if running performance improves.
I am placing my money on bad fuel, bad fuel air mix, restricted air or restricted fuel delivery being your main problems- the saw runs- continues to run- so spark and compression are good, only thing left is fuel/air mix and possibly timing.
If you remove the air filter- are there fines of sawdust and dirt in the carb throat- start the saw without the air filter fitted- does it run better.
Trying to diagnose from afar is a guessing game and process of elimination and if those typing replies have stripped and rebuilt dozens of saws- we often skip over the obvious and mundane.
I will also say I have ZERO experience with canned premix and or ethanol fuel- we just don't have that here where I live. But could it be whatever you are trying to run it on is old, or contaminated fuel that how has a low octane rating?
How long since the saw was shouted a new or at least a thoroughly cleaned air filter? New fuel filter?
Wasted bearings can bind and slow a cranks rotation down- but usually by then they are causing other major problems like cage disintegration and major damage to the cylinder and piston- best way to check those was when the cylinder head was off.
Seized/damaged clutch needle bearing would usually display more as a constant drive to the clutch, or very erratic chain wobble and derailment.
Try stripping the entire clutch side off the saw- no chain, no bar, no clutch and see if running performance improves.
I am placing my money on bad fuel, bad fuel air mix, restricted air or restricted fuel delivery being your main problems- the saw runs- continues to run- so spark and compression are good, only thing left is fuel/air mix and possibly timing.
If you remove the air filter- are there fines of sawdust and dirt in the carb throat- start the saw without the air filter fitted- does it run better.
Trying to diagnose from afar is a guessing game and process of elimination and if those typing replies have stripped and rebuilt dozens of saws- we often skip over the obvious and mundane.
You said you have not used the saw in a couple of years? Did you put the saw away with gas in the tank or did you run the saw until gas in the tank and carb were all burned up? I think you might have a carb problem - the piston and cylinder look fine.
No idea what cleaning your carb entails. Some Stihl carbs should not see compressed air to blow passageways clear of solvent. If you decide to take your carb apart, get a manual and read it first. I'd put some seafoam in your gas - its a cleaner that might dissolve some deposits (if that is the problem).
No idea what cleaning your carb entails. Some Stihl carbs should not see compressed air to blow passageways clear of solvent. If you decide to take your carb apart, get a manual and read it first. I'd put some seafoam in your gas - its a cleaner that might dissolve some deposits (if that is the problem).
I cleaned up the air filter yesterday and started it up with the bar and chain off yesterday and let it run for a bit. I noticed that you could really feel vibration on the saw when the piston is in motion. Kind of like the piston is not operating at the full RPM's.
I will see if cleaning the carb helps. I will also check if rotating the flywheel by hand works OK.
I will see if cleaning the carb helps. I will also check if rotating the flywheel by hand works OK.
RedneckChainsawRepair
Active member
You finding fines in your carb throat from getting by air filter? Just curious. Most folks find them on 490 4910 501. I did too.
Easy fix in pic. Stops it.
Easy fix in pic. Stops it.
That makes at least twice fines in the carb have been mentioned and I am leaning towards that being a major player in your woes.
Ideally you would strip the carb and clean the entire thing out, replacing all consumables with parts from a new carb kit.
Blowing the throat of a dirty carb out with compressed air with the choke butterfly open is more likely to force the dirt/grime/fine sawdust in rather than out and high pressure compressed air plus dirt is not your friend around carb jets and valves.
Looks like the air filter to carb throat "fix" is to use the oring from the 61-272 Husqvarna family that would seal the bearing cap and oil pump to form additional seal at the junction of the two.
As per the picture I guess- in the socket that receives the air horn off of the carb.
Not a "trick" I have ever used or had to resort to- but then I also don't work on this vintage of Echo neither.
RedneckChainsawRepair
Active member
The 272 oring will fit inside the air filter like shown.
Same thing is done on the 590 but with a different oring used to help stop the fines on that model.
On a lot of saws regardless of age, even with the brake set I have seen saws bump over a chain at and idle, and when on the throttle. Maybe confirm that your brake.mexhanism is fully disengaging?Sometimes I forget the simple things.
But was mention above of the chain moving- but too slow to cut anything.
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