Hi Hope someone picks this up as the post is a little old. My neighbor has given me a Ryobi PCN 4040, S/N 05/25 000836 it apparently belonged to his uncle. Looks as though it has done nothing at all, all the paint is still on the bar and the chain is dull but never been sharpened. It has a bar tip protector that I have never seen before which is a good idea for a home handy man saw but no idea how long it has been sitting for. The story so far, initially I thought someone may have accidently put oil in the fuel tank by mistake as the sparkplug was dripping with oil but it is equally as likely that someone pulled and pulled on the rope until they had saturated everything with oil and the fuel has evaporated away. The fuel was also pretty thick and smelled like shellac probably just old. I flushed the motor and fuel tank out with petrol and then added new 20/1 fuel attached a drill and gave it a run for awhile with the spark plug out. It was evident that it was running pretty rich by the stuff coming out of the plug hole. Put the plug back in and ran it with the drill. After about a minute it fired but quit. Removed the plug and it did not appear to be excessively wet but eye sight is pretty poor these days. Tried a bit of straight fuel (no oil) in the plug hole and the motor fired and ran for a few seconds and quit, several times. After each short run fuel ran out of the exhaust and possibly back out of the carburetor throat (not sure about that but a lot of fuel it could have run from the exhaust under the housing and back underneath the carby), Decided to bite the bullet and pull it apart enough to get the details off from the carburetor and maybe get a new one. Unfortunately there is not much information on the the carby unless ZAMA CHINA is significant, there is a small 5 on one piece, I will attach a photo. I removed the plate at the top carby and sprayed a little carby cleaner around the needle valve and other parts and put it back together. The saw started and ran but revved very fast and when you depressed the accelerator it died. Seems to have fixed the flooding excessive fuel problem.
Took it apart again and took the bottom off from the carby and sprayed a little carby cleaner around. Reassembled and this time it starts and revs its little heart out but if you pull the accelerator it does not die. I discovered that if you pushed the accelerator arm closed with a screw driver it would drop back to an idle. Thought I had it licked. Pulled the carburetor out again and shortened the sheath around the accelerator cable where it goes into a holding (mounting) block by about 2mm. (sorry I should have taken a photo. Reassembled and now there is a tiny amount of slack in the cable and you cannot manually close the accelerator any further.
The saw started and revved its little heart out and you cannot slow it down by pushing on the accelerator linkage, (the idle adjustment screw is not touching the linkage) I started it and tried a few different things for no success. I mixed up a new batch of 20 to 1 and added a little extra oil for good measure gave the primer a dozen squeezes hoping to flush the fuel through. It started first pull and smoked a little and revved flat out. I gave it a couple of runs but the same result every time. The high and low idle screws are covered with some sort of plastic yin and yang thing, which I have been reluctant to try and remove. You can only turn them about 30 degrees for the low and 20 for the high. I have tried them in a variety of static positions but don't seem to get a different result. They are pretty difficult to adjust when it is revving and I am a little reluctant to let it rev that high for to long but it does not seem to make any difference.
The gasket between the carby and the intake manifold is not the best but I don't think that would be causing this problem.
Probably the only things left that I can think of is to be a little more severe with the mixture screws and get them out somehow and spray a little carby cleaner in there and then try to get a replacement carburetor.
Open to any suggestions
If I can get a large enough hammer it will run for awhile just trying to get away from me
