My master cylinder went bad.  Got an easy to find replacement part#4060-080200 from eBay.  All went together easily enough but absolutely NO brake pressure.  Multiple attempts at different types of bleeding (manual, vacuum and pressure) led to no change in the feel of the brake pedal.  I contacted the seller and was informed I had the unit installed upside-down.  Unfortunately, this was the way the original was installed and had no play to be put in any other direction.  Guessing this was a "first year released" oversight as my other newer zForces have the lines attached on the side of the master cylinder.

So, I removed the reservoir mounts and the rear line so I could move the cylinder around.  Replaced the rear line and bungeed the tanks so they'd stay upright.  Held the cylinder on its side and began to manually plunge while I had a syphon bleeder attached to a single caliper at a time.  It was a difficult process, but I finally got pressure.  Replaced the cylinder without removing the rear line and did an additional manual bleed.  Pain in the ass but I now (finally) have brakes again on ol' red.

Figured I'd at least share the info in case someone else ran into the same problem.

Finally got to test out the new (for me) zForce 800 at a buddy's property we commonly ride at.  Handled everything Dill's 1000 cc 3 cylinder 200 HP Maverick Turbo could do.  One of the stops is a place along the creek known as "painted rock".

Swapped out existing fluids with 400R/330F mL of the Lucas 75/90 and added the catch can from a motorcycle fuel filter.  I found one that I could see into and open up to empty/clean if needed.  https://www.amazon.com/dp/B0BJ8NLMBS?psc=1&ref=ppx_yo2ov_dt_b_product_details  I removed the little filter basket before putting everything inline with the vent tube.

I wanted to document the installation of turn signals on my new (for me) 2021 zForce 800 trail.  With the 2022 zForce 500 trail the wire colors I tapped into were the same.

Here's the turn signal kit I used...
https://www.amazon.com/gp/product/B09XQKR6RS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Also these will make things a lot cleaner when it comes to the custom wire harness...
https://www.amazon.com/gp/product/B01F54PFLE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B07VX671SM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B08DLK7DRH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B07WWWPR2X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

You'll need to access/locate a few things first.  In the front of the machine near the radiator are the factory plugs for the signal lights (see pic 'Front sockets').  These are what you will use to power the front signals.  If you are fortunate enough to acquire a brand new unit the matching plugs for the lights themselves will be included.  Under the dash display you'll find a plug (or two) that have orange, blue, green, grey and black/brown wires.  This is the socket used to access the factory wiring with the installed switch and relay.  Then in the rear of the machine, visible thru a space in the back panel, you can get access to another plug with orange, blue, green, black/brown, green/yellow and brown wires (see pic 'Rear socket').  This is where you'll tap into the factory wiring to power the rear turn signals as well as have access to the brake signal in case you have a whip light set that supports additional lighting features.  Such as...
https://www.amazon.com/gp/product/B0995YPXCZ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I then modified the harness from the signal kit.  Since it can be powered from the black/brown 12v and green ground wires there's no need to run power all the way from the battery (see pic 'Original and modified turn signals).  On the SxS end I cut off the original plug under the dash and installed the other half of the waterproof 4 pin socket so that the signal right part of the switch goes to the blue wire, left part to orange, ground to green and power to black/brown (see pic 'Console socket modified).

For the front of the machine I changed the plugs to the waterproof 2 pin ones from Amazon to connect the front lights (see pic 'Front signals with sockets').  You will probably need to remove at least a few of the plastic pins to get enough wiggle room to access the fender in such a way that a 3/4" hole can be drilled to install the signals.

For the rear of the machine I ended up taking off most of the plastic panels.  I was doing a full cleaning plus valve adjust and compression test anyway after I got the machine so I had full access to all wiring and mounting points.  You can get away with NOT taking off ANY of the pieces, you'll just need to be a bit more clever/patient when connecting and installing everything.  Again, I just cut off the existing plug and modified the harness to accept the additional lights (see pic 'Rear signal harness).  This (as mentioned before) is the step you'd also use to install a light whip that you would want to control with either the power from key on or power from headlight/running light wires and/or light using the left/right signal or brake wires.  Again a 3/4 hole is made for any signal lights installed.

I would most certainly recommend testing everything each step of the way starting with the relay/switch under the dash.  You'll be able to see the indicators light on the dash with the activation of the switch (see pic 'Console signals factory look').  This will tell you right away if there are any problems with the wiring.  Then, do the same after connecting each light BEFORE fully installing it onto the machine as this will make undoing to correct any mistakes far easier. 

The project can be completed without any of the extra plugs, everything will just need to be hard wired.

My zForce 800 I just got was leaking fuel from the ring after a fill up.  I, too, noticed the retaining ring was a bit loose.  A good snug hand tightening is all it took.

[Late to party post] I just took the z500 out to gas 'er up and when finished I noticed an oil drip that I traced back to the rear diff vent tube.  Doing a search on the matter lead me to this post.  I was traveling on road speeds, so that part matches what others have said.  Also, after opening the fill port I could see the oil level right at the threads, so no filling was needed, suggesting unwanted additional volume due to moisture accumulation.  I'll give the Lucas 75/90 a try and I also have ordered a small filter to put inline with the vent tube as a line of defense.

Well, third time posting in the 'New Ride' section.  Time and time again when choosing a SxS to use for the day I select one of the smaller, more agile machines like the z6 and z500.  So, I decided to trade my 2017 RZR 1000 XP with 3400 miles for a 2021 zForce 800 trail with only 320 miles.  I lose a significant amount of ground clearance, but I feel it is made up for with its increased mobility and higher power:weight ratio.  Looking forward to getting it out to "Dill's" and "The Boogie" (place/event we ride).  So, now it's 3 out of 3 for CFMoto.

With my z500 when we burned the belt it was in high gear and from that point on high gear caused jerking and a lot of noise.  This was due to an acute wear in the contact surface in one specific place that caused the clutch to jump every time it engaged that spot.  Low gear, on the other hand, worked just fine even with the bad place on the drive belt.  Knowing that different gears contact the belt in slightly different places this makes me think it's something similar.  I cannot say with absolute certainty you have a bad belt but the circumstances do seem like enough to at least make it an educated guess.

Are you operating the machine when it happens or is it during idle warm up?  What level does the temperature gauge read when it seems to limit RPMs?

The next day after the paint dried I got everything back together for a test.  Success!

Took the newly repaired z600 back to "Dill's" to try and break it again... I mean ride it.  Seriously, though, I did hit a deep-ish water hole faster than I should have thinking it was just a mud flat.  Later I got bottomed out and when extracted ended up getting dragged sideways a short distance.  These two "events" led to a crack and tear of my passenger side lower a-arm bracket.  So, yet another break in the thin metal these older units use. (First being my troubles with the rear differential mounts.)  I was able to grind the broken one off, measure the hole distance from the still intact opposite side and fabricate a new piece. 

Yeah, that last pic I did my best to show the angles made once the lift got installed.  Being newish to the hobby I was unaware of the potential dangers.  I saw that it bent to accommodate and though all was well... when it totally wasn't.

Added some tables to the z500 and z600.  They lay flat in the back when not in use and use the hitch to attach the support.

During the first ride of the season I noticed an occasional rattling.  It wasn't too hard to find the issue.  The muffler's heat shield had cracked and broken away at one of the mounting points.  A bit of time, metal tape and an unused bracket turned into a 'washer' and all got fixed.

Been busy with the Z600.  One of my rims was missing the STI HD Alloy logo.  So I used some vector art skills and the Cricut to make myself a new one.