OK here's a weird one for the generator thread: can generator heads lose output over time? Seems like one of ours is by far not what it used to be.

What you mean by "generator heads"?

CAn a generator loose power over time?
Generally speaking: Of course.
When it means the engine looses rpm at high load, it will like any other combustion engine:
Problems could be general cylinder compression problems (piston ring or cylinder wall abrasion, valve seats), probles with fuel mixing (gasoline; clogged fuel paths in carburetter, wear, dirt, wrong fuel level/pressure - depends if it uses float or membrane pressure regulation), poor ignition, with diesels low injection pressure (injector replacement), wrong fuel dose range (adjustment), penetrated or clogged exhaust (so wrong counter pressure, eventual resonant pressure boosting not efficient), loose bearing on crankshaft or connection rod yielding lower effective displacement, but mainly compression ratio.
Other source of problems could be failing lubrication (worn oil, wrong oil level), bad thermal management (dirty coolong vanes on the cylinder,...)
As well it could be "false air" affecting the fuel mixing ratio (bad sealing of the intake manifold),...
These do not have to manifest by lower no load rpm, as the governor compensates that by "throttling up". But of course, when it reaches the throttle limit, the rpm sags.

Plus when the generator uses an electronic voltage regulation, it could be as well anything causing extra losses there, so bad contacts, shorts in the winding, in both cases it means the generator needs higher power input for the some output power, so the load, where you reach the power limit of the engine gets lower.

And there could be as well the electrical problems (voltage sags, without rpm sagging): Bad excitation capacitor (induction generators), bad contact on brushes for the excitation winding, failure in main winding (so the excitation reaches it's limit sooner than the engine does)


And once I've met one unusual cause: It was placed so unlucky (in a kind of pit, intention was to limit it's noise; it was part of a small HAM "expedfition"), combined with wet weather caused the exhaust fumes cooled down before leaving that pit, so settle down and practically displaced the oxygen there. Then of course, the engine was not able to keep up...

Generator head...the alternator.
DX'pedition huh? Cool!

It was for the (European?) 2m/70cm(/?) contest used to take place every first weekend in July (dunno, if it is still the case, last time I attended in 1999). We were at Holy Vrch (Palava hills, about 20..30km south from Brno). There were some remains of trenches and pits, likely from WW2 (with wild cherry trees growing from their bottoms, so we know, what the soldiers were eating there at that time:-D).
One of those pits, about 2m wide, 1m deep was nearly perfect to hide the generator and send the noise upwards, so shield it from the tents.
It was the same place, where we had the generator all the time, with no apparent problems.
And it was I think the one before the last I had attended, when it was rather cold and very light rain. And The rain was, what caused to cool down the exhaust fumes so, they stayed inside of the pit to really choke the engine (CO2 is heavier than air with the same temperature, normally it is just the heat, what drives it upwards). Luckily it ends up as very well visible and nastily smelling smoke cloud (improperly burning gasoline means a lot of aromatic hydrocarbons), so nobody was hurt by breathing it or so - I'm pretty convinced the CO and other nastiness have the potential to really cause severe troubles there, when even the engine had troubles with it...
The generator had a kind of "Ground Fault" protection, that stopped the engine when detecting the leaking current, so a piece of wire was enough to stop the engine "remotely" (shorting L to PE wires at the end of the used extension cord)...

That's a really creative shutdown method! Like shorting the hot and neutral to trip the breaker when you can't figure out which one it is!

Well, it was the only safe at that time. Don't forget, the pit was full of thick cloud of exhaust fumes (so much, the engine itself had problems with it, but at that time we didn't knew yet the cause). So approaching there would ask for a severe case of poisoning (CO, lack of oxygen,...), so no one really wanted to approach it to shut it down "normally", therefore we were looking for some way to shut it down without really physically approaching the engine...

The other safe would be to let it consume all the fuel from it's tank, but that would mean waiting for many hours. But we didn't knew at that time it is just choking on it's own fumes, we were expecting some mechanical failure there, it was only after we inspect it and test run it (to find it still in perfect condition), when we may come to a discovery what had really happened...

I didn't even think of the fumes part, I thought it was just a really creative method of remote shutdown!

Well, you should never ever forget that part when dealing with just any type of combustion, otherwise it really uses to have deadly consequences...

We had another snow storm and about 3-day long blackout.  The little Honda was pulled out of winter storage.  Was able to power some lights, a TV and satellite box, and alternating between the fridge and a freezer.  After the last blackout, I already knew it couldn't run the fridge and freezer together, enough oomph to start the furnace, or the voltage to run the well pump (EU2000i only generates 120v while the pump uses 240v).  Attempted to fire up the old Powermate, but it wouldn't start.  Ignition checked out so I checked the carburetor.  Opened the float drain and nothing ran out.  Pulled the fuel line off the carb and had fuel there.  Took the float bowl off and it was all iced up inside.  Deiced it and made sure the choke jet was clear.  Still nothing so I suspect the main jet was plugged up.  Still wouldn't run after the generator was heated for a few hours.  I think I'm going to break down and take it to a small engine shop to have the carb rebuilt and professionally adjusted.  It had developed a flame out the old muffler, which could be from either mix issues or valve issues.  I haven't checked with a compression gauge, but the compression tester in my shoulder says the valves are sealing fine.

For backup purposes, we bought a new 7500 watt Generac with electric start.  Next project will be finding a place to set it up and setting up some sort of transfer switch.

Ouch, 3 day blackout! If you don't mind me asking, just how far out of Fairbanks proper are you? That seems like a really long time for power to be restored...
I've run two freezers and a refrigerator on an EU2000i before, but not plugging them all in at the exact same time...the surge from 3 compressors starting at once kills it.  Plug one in, wait a minute, then the other. 
It won't start your furnace? Wow.  I thought those would...did you try turning the "Eco-Throttle" function OFF? I've run almost everything you can think of off of a 2000i or 3000i.  Washer/propane dryer (Not both at the same time though and everything else shut off), skillsaw, table saw, you name it.  And plenty of preheat and rapid start fluorescents and HIDs!

And also just curious, does your well water test arsenic-positive? I'd like to get a place out in Pleasant Valley/CHSR area and I'm told arsenic can be an issue...and how do I test? Can I go to Spenards or Home Depot or Lowes and get some test strips and do it myself?

Nice, is this Generac gasoline or diesel? It sounds like a nice setup...does it remote-start?  I'd also suggest a transfer switch, you should be able to buy one at any home center...Spenards, Home Depot, Lowes, Sentry, Ace, True Value, etc.  If they don't have what you want look in an electrical supply store...if Fairbanks doesn't have one, I'm sure Anchorage will. 

Ugh, isn't that the most frustrating thing? When you NEED it and it WON'T START?  I agree, take it to a small engine place and have it professionally gone through. 
I laughed out loud at "Compression tester in my shoulder" LOL. 

I'm about 15 miles out.  I'd plug in the freezer first thing in the morning and run it until it shut off.  Being full and not being opened, it will be good for 24 hours without power, than run the fridge the rest of the time.  I always shut the eco-throttle off when plugging in or unplugging large loads.  It wouldn't start the boiler though.  The generator would lug for a second than shut down.

The Generac is gasoline powered with electric start.  I thought of a transfer switch but it would be a huge hassle to put in at this point.  They are great if you plan for them during initial wiring.  My meter box is a combined meter/load center, with a 200 amp main feeding an 8-space bus bar than leading to the primary breaker panel inside.  My plan for hooking up the generator is to mount a 30 amp inlet box where the generator will be, going to a 30 amp back-fed breaker in the outdoor panel feeding that bus bar.  A simple interlock kit prevents the 200 amp main and the 30 amp generator breakers from being ON at the same time.  Than I would mark circuits in the primary panel that would need to be left on when running from the generator, and all others would be shut off.

A benefit of the interlock over a transfer switch is that power can be fed anywhere in the house, instead of a select few circuits, though that has to be done cautiously to not overload the generator.  A drawback is that a light in the house not powered by the transfer switch can be left on to indicate when utility power is restored.  Something you don't get with an interlock.  However, my workaround is that the meter panel has a second separate "main" that is independent of the 200 amp main.  A 50 amp breaker in that space feeds the shop.  Since it is not fed by the main bus, it would not be powered by the generator, allowing me to leave the shop porch light on to indicate when utility power is restored.

There are companies in Fairbanks that do water sampling.  DEC would have info as well.

Out the Chena Hot Springs road or Steese Highway by any chance?

Yeah, I know those do fine 24 hours without power, mine doesn't have constant power either (Also run on a generator, at one point an EU2000i!). 
I've seen the interlocks too I think.  You definitely don't want power backfeeding into utility lines, or utility power backfeeding into your generator!  If/when you do set this, up, take pics and post them! I'd be interested to see how it's set up.

Good to know, I'll just get ahold of ADEC in that case. 

You'll like this then: We have this old Isuzu 3-cylinder that has a burned-up 15Kw Stamford 120/240v head on it that used to belong to my honorary grandfather (It powered his house until it burned up) but we might be sticking a 6-8Kw head on it for the off-city-power place we're trying to buy in Delta Junction.  How well will that start in -40F? (With a glow plug of course). 
Place also has solar panels and 2000w inverter...just a generator as a backup and replacing a couple (expensive to run) 5000w Honda gas units.

Suppose a generator "Head" could lose output over time due to--Weakening PM magnet exciter,Drifting components in field-exciter voltage regulator circuits.In most "heads" these components are easily replaced.However as some others point out-engine problems may be a more likely cause.Engine running too slow or fast.-Or its speed drops too much under load due to speed governor needs adjustment.These are the things I have seen in dealing with Diesel or other engine type Motor Gen sets used as standby or load management power for radio stations.

Oh that sounds like a neat job!  I'm a somewhat serious AM/FM DXer...