This problem began to appear last summer. This generator is lightly used - 4-5 time a year, in a clean environment and each use amounts to burning maybe a tank of fresh fuel.
I began noticing the generator would hunt pretty wildly if a load were switched on (like a thermostatically controlled heater) or the unit was lightly loaded (such as an incandescent lamp) and in the economy mode after warmed up and running with the choke open. The engine would go from near wide open to almost stall and back without end unless I pulled out slightly on the choke. Of course the choke will slowly vibrate back open, and the problem may begin again. Obviously the output voltage is varying all over the place while this is happening. If the choke if held slightly open none of the above occurs.
It seems the engine could be running lean, or making it run rich helps anyway. I know the available fuel around here is now all up to 10% ethanol and I heard from a friend who is a forester that they were having lean run issues with their small 2-cycle motors after they started using the reformulated gas. Since these engines dont have any ability to detect and compensate for Lambda changes caused by fuel formula changes, it would make some sense that it could be running too lean but I am not sure if this is related to the generators behavior or not.
My question is, can the hunting be compensated for with an adjustment? If so it something like that in the service manual? If not is there something else that needs to be done? Thanks.
OK, so I got the service manual. TS guide suggests air leak or plugged jet on carb. I sprayed Starting fluid (ether) in spots around carb and when I hit the area of the return spring for the main throttle shaft the engine speed increased. I pulled off the carb cleaned and and checked the jets and passages - all clean to begin with. But the throttle butterfly shaft has a fair amount of play, like whatever passes for the top bearing for that shaft is gone and air is passing into the carb around the throttle shaft. The manual and parts breakdown dont detail that area so I am guessing no parts are available such as a seal or bearing and I will have to get another carb to make it right.
Since I had to remove the plastic stop cap off the pilot jet to inspect and clean that out I left it off when reassembling it and adjusted it for a no-load Economy SW ON idle without hunting. It took about a turn CCW from its original position however something changed sometime during the spray, disassemble, reassemble process. The engine doesnt want to rev up enough when the throttle control is fully opened and the inverter output drops under high load. If I spray the ether at the throttle shaft the RPM increases nicely then once the ether is used it drops again. I tried moving the pilot jet adjustment for that but it had no effect. Pulling out the choke improves the situation, so it seems to be leaning out under high RPM and load. Hard for me to believe an air leak around the throttle shaft can cause that since it cant possibly account for more than a percent or 2 of the total intake air when the throttle is wide open.
Next step. I confirmed the leak around the throttle shaft by packing the rather loose felt seal and wobbly nylon sleeve bearing with a synthetic grease. It no longer increases speed when sprayed with ether.
While I had it apart again I blew down the jets and passages but didnt see anything, and nothing changed when reassembled. It no longer hunts when unloaded with the econo SW ON and with the pilot jet set wher I have it but turning the jet in about 1/2 turn starts that hunting back up.
I warmed up the generator then loaded it with 900 Watts and the Econo SW OFF. The generator output drops to about 80V with the throttle wide open and the engine is not running at max speed. When I pull the choke out about 1/3 to 1/2 the engine speed picks up and the output is 120V.
The "set the throttle to wide open" tip sounds like a real good one, thanks. I didnt see anyting like that in the service manual and I basically aligned the throttle motor output with the resting position of the throttle when I reassembled it (probably not wide open). I need to get some fresh fuel and try it tomorrow.
I checked the throttle position and it did put itself at wide open when I last shut it off. I fired it up and it didnt seem to reaching max engine speed but before I could warm it up and put a load on it ran low on fuel and havent picked up any today.
Fresh fuel added this PM. Same thing under load (around 900W). The throttle is wide open but the engine will not speed up enough to maintain 120V without some added choke.
I went thru the checklist/tips except for the valve lash. Everything seems good.
I am having hunting issues with an EF1000 also. Mine started when it ran out of fuel. It wouldn't start again, so I pulled the carb a cleaned it . it started, but hunts like crazy. I'm going to pull and clean the carb again, but do you know what the correct setting is for the screw that is a "stop" for the lower limit of the rotation of the throttle plate (if that's the correct name). And secondly, I'm wondering if it really matters if it is working properly. It is set at about 1 1/2 turns backed off from fully in. (fully in being where the spring is fully compressed)
Thanks......I will repost after I clean the carb again
OK...so I pulled the carb, recleaned it (used wire in the jets and sprayed out everything with electrical contact cleaner. then pulled the tank and cleaned it. it had some water and rust. put it all back together and works great.