The purge pump on my Echo CS-400 broke, so I fixed it and recorded it below. While other echo chainsaws (CS-350, CS-300, CS-370, CS-370F, CS-420, CS-5000) may have a different layout, replacing the purge pump is essentially the same.
The weather finally broke two or three weeks ago, and by broke I mean it was probalby 59 in the morning and the high for the day stayed below 90, so I figured it’d be as good a time as any to start cutting some firewood for next year. I gassed-up my saw, topped off the oil, sharpened the chain, and loaded up my wheelbarrow with extra fuel, some wedges and a maul and of course, my saw, an Echo CS-400. I got to the wood lot and got out the chainsaw, ready to go. I pulled the choke and jammed the purge pump: the delicate little rubber bulb popped.
Not wanting to turn around and head in as soon as I got out there, I decided to see what would happen if I tried to use it with a busted bubble. I got the saw to fire up, and it seemed to run normally, but as soon as I put a load on the chain, it would stall out.
I came inside and fired up the ole Amazon. A number of these small parts are interchangeable between different Echo models (the package I picked up covered Echo CS-400 CS-370 CS-370F CS-400F CS-420ES CS-5000 CS-3500 chainsaws.) I settled on a package that contained an air filter, fuel filter, spark plug, vent, and two purge pump bulbs.
It was an easy enough fix to replace, the longest part was probably removing the screws from the housing, but otherwise it went fairly quickly. I recorded the whole thing, uploaded it to YouTube and have linked to it below. This fix also works for other Echo chainsaws, although the layout may be slightly different.