Echo CS 400 chain saw wont run

[Snipe Hunter]

That's classic signs that the carb is dirty. 

+1

Have a recurring issue with my 2-stroke outboard. It gets gunk in the bowl around the jet valve. The gunk is from deteriorating fuel lines caused using ethanol in the fuel.

Once the carbs are cleaned it's fine.. until next time.

Non ethanol 2-stroke fuel is sold at hardware stores in gallon cans. Not economical in an outboard though.

[Bob10]

I use TruFuel for my 2 stroke tools.  I like that I can let them sit with gas in them and nothing turning to goo.  The last thing I want is to need a tool and have to spend time repairing it instead of using it.  I can't tell you the number of chainsaws I have seen people toss out because the damage ethanol caused.  I have picked up more than a few, replaced the fuel line and cleaned out.  Beats the hell out of buying them

[pprobus]

I use TruFuel for my 2 stroke tools.  I like that I can let them sit with gas in them and nothing turning to goo.  The last thing I want is to need a tool and have to spend time repairing it instead of using it.  I can't tell you the number of chainsaws I have seen people toss out because the damage ethanol caused.  I have picked up more than a few, replaced the fuel line and cleaned out.  Beats the hell out of buying them

I had it happen long before ethanol was put into gas.  Old gas is bad news whether you have ethanol or not.  The only thing I may be able to blame on ethanol is that soon after it started being added to gas in the early 2000's, the McCollough chainsaw and string trimmer my dad passed down to me had the primer bulbs break (my wife to this day still finds it suspicious it just happened to be around Father's Day, one year the trimmer, the next the chainsaw, or vice versa
).  Since McCollough was out of business and they were 20+ years old by then anyway, I just upgraded to Echo equivalents rather than try to scrounge parts that fit or try to make parts fit, while I couldn't avoid it with the string trimmer, I chose the chainsaw because it didn't have a primer bulb.  Like I said, just plain gas sitting in my scooter's tank and carb over the winter (roughly late Sept/ early Oct, until April/May the following year) was enough to give noticeable issues with how well it ran.  After using the, "run your carb dry" method, the old gas would make the scooter run a bit rougher until I used it up, new gas made the scooter run great without changing anything else.  But if I didn't run the carb dry, the carb would need to be adjusted to run close to right again, or cleaned to run right without changing the settings.  I think most of the blame put on ethanol in gas is just poor storage practices by owners that would have resulted in issues whether there was ethanol in the gas or not.

[Snipe Hunter]

Ethanol or no ethanol, old gas gums up carbs. New gas doesn't get rid of the varnish.

I hesitate to run carb cleaners through small 2-stroke carbs. I was told not to do so by someone I trust so I don't do it. Said it can damage the engine because the solvents make the oil in the fuel not stick to the piston and cylinder walls so it doesn't lubricate well enough when running. Makes sense to me.

Chainsaw carbs are very simple and easy to clean. You can take it off and soak the whole thing in carb cleaner or injector cleaner and blow it out with the butterfly valve open. Wouldn't use real high pressure. Your just blowing out the gunk and drying the carb. Or you can simply take off the bowl and clean it out (my preference). I don't like to adjust anything but if I did, I'd make real sure that I ut it back together exactly the way it came apart. Count the turns on the adjusting screws and write it down. Usually you can re-use the gaskets without issue. I think Echo uses rubber gaskets. I also now you can replace most chainsaw carbs for about $50.00. 2 stroke carbs are very simple but if adjusted too lean, they can burn up your piston. Sometimes when carbs have the problem described above, leaning them out makes them run better (not stronger though). Don't fall for it. Set it to factory suggested specs.

[JosephP]

Ethanol or no ethanol, old gas gums up carbs. New gas doesn't get rid of the varnish. Yep.

I hesitate to run carb cleaners through small 2-stroke carbs. I was told not to do so by someone I trust so I don't do it. Said it can damage the engine because the solvents make the oil in the fuel not stick to the piston and cylinder walls so it doesn't lubricate well enough when running. Makes sense to me.  I haven't heard that...but makes sense to me too.  The cleaner is designed to dissolve oils.  I am a little suspicious that a few squirts will do much, but I can certainly see where using it regularly would cause lack of lubrication.

.....I don't like to adjust anything but if I did, I'd make real sure that I put it back together exactly the way it came apart. Count the turns on the adjusting screws and write it down. ..... Don't fall for it. Set it to factory suggested specs.

factory specs are not determined by position of the screws or number of turns (if it were that simple, they wouldn't put the screws there in the first place).  The screws are adjusted to set specified RPMs...so to tune a carb correctly, you don't need to count turns, you need a tachometer.

[Snipe Hunter]

factory specs are not determined by position of the screws or number of turns (if it were that simple, they wouldn't put the screws there in the first place).  The screws are adjusted to set specified RPMs...so to tune a carb correctly, you don't need to count turns, you need a tachometer.

If it ran right at those settings and they haven't been changed, the settings probably aren't the problem. That's why I'd count the turns and re-set it the same after cleaning the carb. My guess is there's gunk in the screen filter in the carb, gunk in the needle valve or gunk in the reed valves inside the carb. I've never opened an Echo carb. In my experience many small 2-stroke carbs don't have a float (which would have to be adjusted to factory settings if it did) but have a couple diaphragm gaskets and a diaphragm with stamped reed valves under the cover/plate. Not sure if a rebuild kit is available but if not, opening everything up and cleaning it out should fix it.

The little filter screen can easily be damaged trying to remove them. I spray carb cleaner through them. If the opening is big enough, you can take an acid brush with the bristles cut short and clean the screen out with carb cleaner. They get something like a thin layer of jelly in them. It's a lot easier to clean these things opened up. There's usually a gasket on one of the covers that gets stuck to the cover. I just leave it in place as opposed to risking tearing it. One of the diaphragms (under the valve cover) is the fuel pump iirc. There's probably a gasket attached to it They usually separate fairly easily for cleaning. It's the other cover that gets the gasket stuck to it.

The pressure of the carb cleaner should clean out the carb sufficiently. Make sure you have some goggles. Spraying carb cleaner in those little holes can make it shoot out in some odd directions.

Also, there's probably a little screw holding in the needle valve and spring... might have a little rocker arm there. Press your finger over the valve/spring assy when unscrewing it so it doesn't fly across the room.

Pay close attention to the reed valves stamped into the diaphragm. They may look fine but they can get stuck in place. Just be real careful separating it from the carb body.

I usually soak the valve assy itself before trying to clean it. If the orifice is big enough, I use a guitar string or a welding tip cleaning tool to push through it. If it isn't big enough, I have to rely on air pressure.