I doubt all XZ20R's are like this.  Luck of the draw I suppose.  
Just thinking out loud here.  Most fuel tanks have a screen at the neck, right?  This one didn't when I picked it up.  
The screen in the hydraulic tank - totally from the factory.
The contaminates in the fuel tank - I'm not so sure.  I'm wondering if someone dropped something in the fuel tank after it left the factory.  
Who knows.

I wish I liked tinkering with stuff. Looked like you had a productive day, I would have been a little more grumpy.

Wow! Not what one would expect. I just bought a Huayee machine which is supposed to be several cuts above most of the lower end minis. i've been in touch with a Huayee engineer who claims no need to remove/replace fluids. Man I hope he's right,  I ain't lookin forward to doin all what you did. Thanks for the vid!

Really glad I saw this video. I just got done checking my XZ20R and sure enough the suction filter was just laying loose in the tank.

Also, you should look into running an ATV battery. It really frees up a lot of room in front of the engine cooling fan which is desperately needed.

It seems like some of these mini Chinese excavators are just slapped together on basic principles alone and really no sub-engineering has gone into them.

Just a heads up ... Info type of thing 👍 . Hyd cyls have a piston on the end of the rod . Pressure one side and it goes the opposite direction , fluid comes into the non pressure side . Vice versa ... So there is no advantage in positioning the rod in the cyl . Best to change Hyd fluid several times 👍

By the way, at timestamp 1:12 and 1:13,  your finger almost exactly points to the hydraulic piston (and you can see the curved mental pipe that the hydraulic hose connects (that connection is a failure point). If you inspect the piston assemble (you will notice that the hydraulic tube is connected to a thin metal or (cast iron) looking tube that curves into the piston assembly. If you look at the weld, just as that point where the tube curves into the main piston, you will notice (and it might take a few session) that then the hydraulic heat up, the paint will chip, and you fill find, rust. Which means, that at some point the joint (on the piston) where the metal tube connects will fail. And finding a replacement will be a nightmare. I am still baffled at why they did not just put the hydraulic tube connect directly into the main piston? Most likely for the sake of cheap production and fast assemble. I carefully scraped the rust off the connection (praying that the hydraulic tube will not suddenly fail and squirt hydraulic fluid every where, and have resorted to (after scraping the rust off, as best as possible) cleaning the area and then using (JD-WELD)  around all of those connections (As cheap insurance). In the mean time, I have seen searching for people dumping the old Chinese excavator or ones that failed, just so I can harvest these hydrophilic pistons,  because when these things start to fail, there are no replacements to be had, and the only other alternative, is to buy another excavator with the same model and keep it for part. I also took the Canopy off my mini-Chinese Excavator and frankly, probably will never put it back on.

I told you about the dirty tanks lol

It is like buying a fixer upper thats new lol. Hard to beat them for the cost if you are willing to do some mechanical work.

One great mod as long as you have the fuel tank out is to go ahead and enlarge the fuel tank... These machines have very short run times due to the thirsty engine small tank combo... The fuel filter can be gotten for just a few bucks... I switched mine to a goldenrod water block filter also you will need to add fans to this machine I have this exact machine and it had overheating issues it needs auxiliary fans blowing from right side to left side as the battery location prevents the engine from getting good cool airflow combined with the poor exhaust design that traps massive amounts of heat in the engine bay

I can only speculate, but I wonder if your fuel was starting to develop algae.

Check the slew bearing bolts in the YNT18 ASAP there are 6 lower and 6 upper all the uppers in my 18 were barely tight and 4 of the 6 lower fell out at less than 20 hours use time. I purchased new at auction. Bolts are M16-2 x 65mm 12.9 and take a 14mm hex.

You would think the union built this

el aceite de los motores de las orugas, como se limpia? siendo la parte más baja del circuito, seguro todas las partículas metálicas reposan ahí.

That just is one of many reasons why I ended up to Rippa! Both tanks are composite, not some bad welded rusty boxes! And they are vertical standing! And they were clean! What is with people, why you want that cheapest junk? I want the best that money can buy! 🤣

Really sad all this work needs to be done but it is what we get for the price of them.

I  am hung up between this unit and am sdlanch me20