There are people that claim Harbor Freight generators are throw away junk. While the harbor freights have not been trouble free, they are not throw away. The issue seems to be that vendors and repair centers just dont want to work on them. Both HF's were not purchased new. They were from a damaged freight insurance sale outside of the venue of harbor freight. Having said that as of December 2015 I have over 1600 hours on HF #1. I use HF #2 as my backup. If #1 has a problem I swap #2 in unti I have the first one running.
HF#1 had a head failure arounde 1000 hours. The problem was the result of a bad valve guide retainer that broke during the first 100 hours but was not obvious until the valve guide had wallowed out the exhaust valve guide over the next 900 hours. I replaced the head with an aftermarket Honda GX390 head.
One of the complaints of the Harbor Freight and other clone generators is unavailability of parts. I've not had any problem. Every replacement part that I have needed to date has been easily obtainable via Amazon buying parts for a GX390. The generator head I have had similar success with. Brushes and voltage regulators are readily available on amazon.
So its not a matter of them being throw away. It is a matter of finding either a competent mechanic, or do it yourself(my method).

Service Note 1: Nov 5, 2011 - While doing a panel check I found that one array was dead. One of the AP-120's had a spot on the back covering about the size of a cigarette burn. Apparently there was a bad connection from the factory on one of the cell interconnects. I was able to fix it by cutting through the covering and silicone. The burnt spot looked to be overheated but cleaned it up and resoldered. The cells on these panels have 2 tabs per side. Checking the connection on the other tab and it was open. Resoldered that and fingers crossed that it is corrected.

Service note 2: Nov 2, 2013 - While doing a monthly battery water check two of the cells had not used any water since last month. Checking them with a hydrometer and s.g. was barely able to float the float. Two bad batteries at 4 1/2 years, not the life expectancy I was wanting. Originally I rearranged my bank to a 6 pack in hopes to make it till spring with the remaining batteries. That did not work out and I will not be using US Battery again. I had 4 Deka L16's previously and they lasted 8 years.

Sept 2, 2016 Relaced 8 GC2 Duracell/DEKA batteries that had been installed Jan 2, 2014 with Duracell/Deka 8L16's. The GC2's were starting to bulge and go through water rapidly.

Service note 3: Oct 25, 2014 - AP-120's now I know why they went out of business. Found the wiring block on the back of one of the panels dangling. The silicone caulk had separated from the box. Reglued with additional silicone.

Service note 4: Oct 2014 - The higher time Harbor freight generator for the last couple hundred hours had been leaking oil. Case bolts were slightly loose and was able to retorque them. Then something catastrophic happened. Engine surged a couple of times and died with a single pop backfire. I went out to check it and found oil sprayed time on engine about 1168 hours. Problem turned out to be the PTO crankshaft seal had dried out and blown out. Replaced the seal which was harder than it should be as it required disassembling the generator head to get access to the seal. Back in service as of 10/25/2014.

Service note 5: August 2015 - While running the high time Harbor Freight at just over half load 3500-4000 watts the generator lost voltage on one leg. Taking the generator head cover off one of the stator neutrals crimped connectors had overheated causing the wire to break and burnt insulation off of the wire for several inches. I was able to repair the stator by cleaning the copper and splicing in a short section of wire.

Service note 6: December 2015 - HF #1 with about 1615 hours on it refuses to start on electric start. Cranks, sounds slow but will start normall on rope start or if I prime it with burst of LP first. Swapped HF #2 until this weekend. HF1 would crank up to 40 seconds and not start I removed the starter and end bearing is very loose, and noisy when spinning out of the engine. Swapped starter with HF2 and not HF1 starts with about 14 seconds of cranking. HF2 starts just a little quicker but has 1300 less hours on it. Ordering a new starter.

Service note 7: Dec 28, 2015, generator stopped running after blowing enough oil out what I think was the rear crank seal. Having extreme difficulty getting the generator armature off to change the seal. As much as I did not want to buy another generator with it being mid winter I couldnt risk being down to one functional gen. I"ve not given up on HF1, at 1700 hours, but I need to step away from it for a while.

Service note 8: Jan 12, 2017, HF #2 with 657 hours was starting hard and lugging down at half load. Increased noise on the intake side and more oil blow back out the breather. I pulled the head and found the same problem as with HF 1, the exhaust valve guide has significant wear. I swapped the head with the head from HF #1. It is starting quciker, and quieter with the swapped head.

Service note 9: June 8 2018, Predator 1, after running for a half hour lost AC output. Tracked it down to an open exciter winding. This takes this predator out of service at 1231 hours, aggravating.
Update June 29, 2018: Pulled the stator off and cut the wiring loom off one side so i could lift the exciter wires and unwrap them. Discovered that it had a kink/corrosion that had broken right where the ALUMINUM stator windings were soldered to the short copper harness. I spliced this with WAGO electrical lever splices after cleaning up the wires and then zip tied the wiring back down. Initial short minutes test it is producing power again. Will put it back as the primary and see how it goes.