I keep seeing lots of suggestions that could happen were the spark plug still in. The first thing I noticed in the OP was that @bcs001 already checked the obvious possibility of compression relief. So I won’t bother with unrelated stuff about country of origin or electrical issues that would be easily solved by anyone with real electrical expertise. I’m a retired electrical engineer who grew up on a farm where if we couldn’t fix things, they probably couldn’t be fixed. Couldn’t afford technicians and were probably a bit too stubborn to pay for them anyway. I also owned an air cooled VW for 35 years so have a bit of experience with air cooled engine quirks and differences.
This sounds more like a failed bearing, but no way to know whether generator or engine is the source of the problem unless it’s separated and each checked for the stiction issue. If it’s an open frame machine, hopefully it won’t be too much trouble to separate the generator from the engine. Most small generators have only one bearing in the ODE (opposite drive end) and rely on the output shaft bearing to support that end of the rotor. Without the spark plug installed it should spin freely without any resistance other than the inertia of the generator rotor and friction of the engine components. The generator rotor tail bearing is usually either roller or ball bearing because of rotor speed being high enough to toast a sleeve bearing without forced lubrication. The internal bearings in ICE’s are nearly always sleeve bearings because of having forced or splash lubrication and they’re a lot easier to assemble than roller/ball bearings inside a tight space like an engine. Certainly more cost effective for manufacturing. What I read in the OP’s description of symptoms is pointing to a bearing failure in progress. A metal shaving or a little casting sand has taken out more than one engine that was otherwise top quality and preferred name brand. Chit happens, especially if you’re like me, and wouldn’t have any luck at all if it wasn’t BAD luck
This case might be a good argument for extended warranty (basically a form of insurance). But, meanwhile, since that didn’t happen (and would have been no different for me possibly) draining the oil from the engine and running a magnet through it would be a start (and a strong indication that the engine is already FUBAR). However, if the damage is limited to galling of the babbited bearings or milled aluminum parts, chances are you may still need to open up the crankcase and pull out internal parts of the engine for a complete visual inspection. It’s possible that it will be necessary for repairs anyway, so having it apart is halfway to repaired labor wise. A stiction issue on any internal combustion engine with the spark plug removed is NEVER a good thing. If it is easier to r&r the head, that would let you examine the cylinder. That could also be done even quicker with a bore scope through the spark plug hole. While you have the oil drained, a bore scope might show shavings that didn’t come out with the oil, but the bore scope won’t really help examine bearing surfaces. IMHO, the engine and generator should first be separated and the source of the friction identified. Whatever the cause, the testing you’ve already done has eliminated any possibility of compression being the culprit, but hasn’t ruled out a broken ring or bearing. Either of those will be terminal for the engine if as you say the stiction is getting worse.
The starter “dropping out “ is probably due to excessive starting current causing enough voltage drop in the starting circuit. Until you identify the friction issue, no point in messing with the starter. You already stated that the pull-start was difficult to use.
My opinion or guess has nothing to do with my experience, but I think my experience with both ICE and electrical machinery (50 years in the industrial service industry) might affect it. You’re on the right track with the testing, but may have to go farther than planned. If you’re financially sound enough to be able to replace it, that could certainly be the better alternative to repairing it, depending on your skill level with small engines and generators.
This sounds more like a failed bearing, but no way to know whether generator or engine is the source of the problem unless it’s separated and each checked for the stiction issue. If it’s an open frame machine, hopefully it won’t be too much trouble to separate the generator from the engine. Most small generators have only one bearing in the ODE (opposite drive end) and rely on the output shaft bearing to support that end of the rotor. Without the spark plug installed it should spin freely without any resistance other than the inertia of the generator rotor and friction of the engine components. The generator rotor tail bearing is usually either roller or ball bearing because of rotor speed being high enough to toast a sleeve bearing without forced lubrication. The internal bearings in ICE’s are nearly always sleeve bearings because of having forced or splash lubrication and they’re a lot easier to assemble than roller/ball bearings inside a tight space like an engine. Certainly more cost effective for manufacturing. What I read in the OP’s description of symptoms is pointing to a bearing failure in progress. A metal shaving or a little casting sand has taken out more than one engine that was otherwise top quality and preferred name brand. Chit happens, especially if you’re like me, and wouldn’t have any luck at all if it wasn’t BAD luck
This case might be a good argument for extended warranty (basically a form of insurance). But, meanwhile, since that didn’t happen (and would have been no different for me possibly) draining the oil from the engine and running a magnet through it would be a start (and a strong indication that the engine is already FUBAR). However, if the damage is limited to galling of the babbited bearings or milled aluminum parts, chances are you may still need to open up the crankcase and pull out internal parts of the engine for a complete visual inspection. It’s possible that it will be necessary for repairs anyway, so having it apart is halfway to repaired labor wise. A stiction issue on any internal combustion engine with the spark plug removed is NEVER a good thing. If it is easier to r&r the head, that would let you examine the cylinder. That could also be done even quicker with a bore scope through the spark plug hole. While you have the oil drained, a bore scope might show shavings that didn’t come out with the oil, but the bore scope won’t really help examine bearing surfaces. IMHO, the engine and generator should first be separated and the source of the friction identified. Whatever the cause, the testing you’ve already done has eliminated any possibility of compression being the culprit, but hasn’t ruled out a broken ring or bearing. Either of those will be terminal for the engine if as you say the stiction is getting worse.
The starter “dropping out “ is probably due to excessive starting current causing enough voltage drop in the starting circuit. Until you identify the friction issue, no point in messing with the starter. You already stated that the pull-start was difficult to use.
My opinion or guess has nothing to do with my experience, but I think my experience with both ICE and electrical machinery (50 years in the industrial service industry) might affect it. You’re on the right track with the testing, but may have to go farther than planned. If you’re financially sound enough to be able to replace it, that could certainly be the better alternative to repairing it, depending on your skill level with small engines and generators.
