Greetings folks!
I got this saw in 2015, but in terms of regular work in real time, you could say it's only seen about 3 months of use, so not old and should be in prime condition still.
I had in the past a lot of trouble starting and running it, and it stalling in the middle of a cut, and wasted money on trying to get a dealer to service it but with no result from that quarter.
So I bit the bullet and removed the Zama C1M-W26C carburettor myself and took it apart. AFAICT all the gaskets and diaphragm, checked carefully under magnification, are in tip-top condition, so I sprayed carb cleaner copiously down the mixture screw holes and other accessible passages to make sure all they were clear, particularly through to the three idle ports in the venturi which lie under the welch plug. I then re-installed the gaskets, diaphragm and reservoir retaining plates. The only other work I had to do was Bondic weld the black plastic cam lever for the actuator for the auxiliary air intake valve (It had split slightly on its mounting post), and replace the primer bulb fuel line from the upper reservoir (some very light seepage around the bulb housing).
After this work the saw ran very well; when warm I could stop it and start it with the softest of pulls. But it's performance has been variable. I now try to start and run it briefly each day. Sometimes it starts first pull, sometime it takes a few more. Usually I have to initially screw in the idle speed screw about two turns and I find starting without choke is the best. Once going I can then screw it out again until the chain stops. But careful observation in bright sunlight shows that during running I'm getting bubbles of air forming in both the main tank filter to carb lower reservoir line, and also in the priming circuit. However there are now no signs of any fuel seepage or leaks anywhere - the floor of the housing above the tank is completely clean and dry. So unless it's a tank-not-being-full problem, how is this air getting into the lines?
I suspect that air in the system is causing sudden fuel starvation after idling nicely along for a while, or upon opening the throttle quickly (normally acceleration response is excellent). Sometimes I can force it to die by simply tilting the saw over to the right, although this is not all the time. I suspect that this tilt causes air in the carb upper reservoir to rise to the left, at the highest point, right near the opening into the idle circuit passages and so the fuel flow stops.
I tweak the idle mixture screw to optimum each time I run it. The performance inconsistency is intermittent; I have had certain days of beautiful and responsive running, and others where it's a beast to get going or keep going.
