Tecumseh vs Preditor, Briggs intec type motors

The engine shown in the picture is a 'vintage' engine. The last engines Tecumseh made were OHV instead of the flathead style you have. That fact makes the vintage of your generator & engine more than a few years.
Personally, the Tecumseh engines are good, but I'd prefer the efficiency of an OHV engine, along with the setting on 'inverter' generators that allows the engine rpm to drop below 3600 when demand is less than peak. Older style generators require 3600 rpm to produce 60Hz AC power. That means they must be twirling pretty good even when demand is low.
I had a late model Tecumseh 'LeMans' or 'Enduro' (can't remember) OHV that I really liked. It just sounded as if it enjoyed running along cutting the lawn, and I had zero problem with it.
Finding parts for you Tecumseh may be a problem as they are no longer in business. Only aftermarket or NOS parts are available currently.
I am of the opinion that the imported engines are of good quality for the most part. Many are perfect clones of Honda designed(Honda manufactured in Chinese plants, the clone during off-hours?) engines. Later models are not exact clones any more, but have copied the general 'style' of the crankcase, cam, valve train, etc.
Treat them well, break them in properly, and they will likely give a good long life. Right now, there is not much choice(if any) for USA manufactured engines. I do think the total cost for overseas manufacture is trending up, and the premium to manufacture in USA is decreasing. Some plants are re-patriating, though I don't know exactly who.
Tecumseh is likely gone forever, along with Clinton and others. Briggs has Chinese production, and many non-branded engines are being used in OPE.
New non-inverter generators are likely more efficient, and have decent quality engines, IMO. Their price seems to have dropped like a rock. The older model you obtained should have been pretty low cost as it seems they are being discarded or sold in favor of new OHV engines and gen sets. See also: craigslist
tom

They don't want sparks from the PG&E high tension wires to set things afire. I think PG&E may have gone a bit short on maintaining their right-of-way, clearing brush and limbs that are a bit too close. From reading, I understand that the 'Camp Fire' may have been caused by the wires sparking in winds...
I'd sooner they cut the power if it avoided torching acres...
The Tecumseh should work fine, but it will be a bit thirstier than others. It might be worthwhile to check the valve clearance before you get into 'fire season', as it is not something you want to be doing under pressure. Given ignorance of use and history, I might even remove the cylinder head and inspect the valve seats and seating area on the valve tulip. Touching up the seats with some grinding compound will help the engine run better when put to use. If the clearance is too tight, it may be difficult or impossible to re-start the engine when it is warmed up. The heated valves/seats/engine block will close up the tolerance, and perhaps reduce effective compression when pulling the rope starter enough that it is hard to get going again. Been there with an old push mower, and was ignorant of the cause.
Again, more preparation, I'd drop the float bowl and inspect for 'stuff', and take a good look into the fuel tank for stuff that could plug the outlet. Inspect the fuel filter. Change the oil, and put it on the shelf or under the bench for use later.
If you keep containers of fuel, I'd suggest dumping them into the car/truck fuel tank and refilling with fresh on about a monthly basis. Small engines don't tolerate stale fuel nearly as well as multi-cylinder engines with starter motors.
FWIW, you might want to look at the HF raw water pumps, rather than the energy loss going through gas>generator>electric>pump series. They may have other water pumps, I don't know, just noticed the raw water pumps.
tom

I would be a bit leery of using a hot tub pump to lift water from a well. My experience is with pool pumps, which have to be primed, even when just a little higher than the level of water in the pool. Priming a hot tub pump to get it to lift water from below would be a bit questionable in my mind. They are a bit different(?) from pool pumps in that they are used to circulate and run 'jets'. Pool pumps also have their outlets, which are similar to the jets.
You may want to look at amazon, as I have seen multiple units for less than $200, brand new, that will produce enough to run several pumps at a time. A 3.5hp engine may not produce as much Kw as you need for several pumps. I'd check the tags on the pump motors for their power requirements.
Flathead engines need valve adjustment due to wear of the valve & seat. That wear will move the stem downward, towards the cam lobes, which will decrease clearance.
Proper clearance will be given in a range, such as .005-.009". As the valve wears, the clearance will close, and the only way to increase clearance, and get back into the proper range, is to shorten the valve stem. A valve stem is ground or filed shorter, checking very often as it is 'adjusted', until the clearance is in the suggested range.
Most people will use a bench grinder, applying the end of the stem perpendicular to the face of the wheel. Grind off a bit, put back into the block and measure, tappet sitting on the heel of the cam lobe. More or less. This would be done after re-surfacing (valve grinding)the valve seat and the valve face, or lapping them using compound.
A flathead engine cannot produce as much hp per unit fuel as an ohv, generally. The flow of air through the engine is more restricted in most cases as the passage from the combustion area(over the piston) to the exhaust and intake is more restricted than the more direct passages of an OHV engine. So they use more fuel. The pressures of the EPA, CARB, etc pushed the small engine manufacturers to produce OHV engines for the push/self-propelled mower market, not fuel economy or lack of power. The OHV engines run cleaner as they can clear the combustion area better. I think. Most lawns would be fine with flathead, but external pressure has forced a change. When running a generator, you might be concerned more with fuel usage than when running a mower for an hour or so weekly.
If the engine has good compression, and will re-start readily when hot, it may not have had enough use to need anything done to the valves at all. I would definitely do a test of the pump equipment I was counting on for use during an emergency.
tom