I have a Yamaha ef2600 generator: It is used about 12 hours each day. I change oil in it about every two or three weeks. I live in a foreign country and this is my only source for power other than the batteries that it charges. The fuel here is extremely bad quality so I constantly run Fuel Cleaner through.
It began to smoke so I put new rings in. I also cleaned the head and the piston that was covered in thick carbon.
It ran great for about three months and now it will not hold the throttle. I mean I have it Idling at 120v and under a load it drops way down. If I touch the governor it will go up but not stay, if I advance the governor it is fine till I turn the load off and then it throttles way high.
I cleaned it completely today, it already had a lot of carbon on the piston and in the head. I cleaned the valves and reset them to .102mm; I set them again after it ran for a while.
It still will not hold 120v I do not have a compression tester right now. I am wondering if I may have put something back wrong.
About the high rate of carbon buildup, that is what you wll get with a flathead type engine running on poor quality fuel. The combustion process is not as efficient as it is with an OverHeadValve (OHV) engine because of the inherently low compression ratio and larger (detrimental) heat absorbing combustion chamber surface area compared to an OHV engine. Seriously saving for a newer OHV inverter genny should be your top priority as it will have a much brighter present and future.
The unresponsive throttle symptoms you describe happen when the external governor arm is not correctly adjusted
the internal moving parts such as the plastic gear and/or flyweights can be damaged/broken. This would be true if the latest bad symptoms happened 'all-at-once'.
Lets start with the easy shots first: adjusting the external governor arm setting point. The mounting pinchbolt that locks the arm to the governor shaft may have come loose from normal vibration or after being inadequately tightened or if the arm received a heavy bump from something falling on/against it (That has actually happened with a customer!) You readjust the governor arm by first loosening the governor arm's shaft pinchbolt just enough so you can wiggle turn the governor shaft's flat end with pliers while holding the governor arm. Then you move the throttle arm so the carb goes to the full throttle stop and hold it there. While still holding full throttle with the arm, turn the governor shaft in the same "toward full throttle" direction until it is stopped by the internal governor mechanism. Then tighten the pinchbolt while you maintain both parts at their respective full throttle stops. You are done!
When I took the generator apart this time, the gear for the governor had not meshed right on the cam. Not sure where it was riding. The generator is responding good now EXCEPT that, there is a high pitched squeek or scrape when a load hit it, only for a second and only till it adjust. Not sure what that is. Normal running is fine just that moment when the load hits. ANy suggestions?
traskgr, Given the very high run time hours this genny has seen I would say the crankshaft bearings are worn so much that the scraping/screeching is the steel frame of the motor's ignition coil rubbing on the flywheel. That contact will leave obvious scoring marks. The ignition coil is easily readjusted so it won't scrape. The other place is the alternator rotor scraping against the stationary steel stator poles because of bearing wear or loosening of the alternator bearing support. There can also be silly things like engine/alternator alignment dowel(s) left out on reassembly, erasing the required running clearance on one side.