specifically 2022 Cforce 800XC.
2854 Miles, a minor clutch tweak (softer CVtech primary spring and 18 gram weights instead of stock 16 gram and factory spring) and a RJWC header.
Ive been quite studious about checking for signs of lean conditions and havent seen any of the characteristic signs of lean conditions at all.

No issues til a week or so back.
My mileage dropped sharply all of a sudden.
From 18-20 consistently unless I was hauling or in 4 wheel. and averaging 17/18 with some minor clutch tinkering.
(I watch the mileage a lot because when I hit the woods I usually go over 100 miles consistently)

I had time over my weekend to start investigating and checking.
I noticed my oil level seemed markedly high and smelled pretty heavily of gas.

I changed it about 120 miles or so ago and havent ridden really hard lately, and its been way to rainy and cold the last couple weeks to ride so its only had about 30 miles on it in the time period where I noticed the fuel consumption/mileage drop

So I drained it again and poured some off into a clear plastic bottle.
My almost new synth oil is pretty syrupy looking.
About like worcestershire sauce and a bit thin feeling.
I'm guessing from combustion particles washed down with fuel.
Zero sign of metal particles or any debris . . just exceptionally dirty looking and stank of fuel.
Its NEVER looked dirty like this even during break in.

The bike RUNS FINE. I'm waiting on comp tester extensions and a leak down tester to verify ring
condition but what I suspect is that my injectors are jacked up and leaking fuel into the cylinder, which is running past the rings into the sump.
I can go out and start it just like normal, it idles up until it warms up and slowly drops down around 1350, which has been normal for this bike since I bought it new.
It isnt lacking power or response but it does pop a bit out of the exhaust which is new and just started about the time I noticed the mileage drop.
Before it barely ever did and then only whe sharply decelerating coming down my backyard (if you have seen any videos of my yard ist fairly steep in places) which would be pretty normal.

I noticed intermittently that it would take longer to pressurize up when first starting it and was pressurizing up nearly everytime I started it.
Previously it had to sit a bit for it to need to build pressure, suggesting the system was (or had been) holding pressure consistently.

So I changed the oil out and put fresh in (without changing the filter) let it sit and checked the level, topped it up and let it sit for about 1/2 an hour then checked the level (a hair under the line) before starting it.
I took the dog for about a four mile run and came back to the house, parked it and let it sit for awhile for the oil to drain into the sump again.
I checked it awhile later and it was right at the line where I filled it too.

I checked it this morning and its about a 1/4 inch up the dipstick . . . and stinks of fuel.

since the injectors are the ONLY point at which fuel can enter the engine my logic suggest the injectors are sticking open allowing the residual fuel to drain into the engine and the sump?

Again I'm waiting on some extension adapters so I can do a compression test as well as a leak down test.
The drain plug magnet was metal free and absolutely zero glitter when I drained it . . and I let it sit draining for an hour.
I even panned the residue around the drain pan checking for shimmer.

Does it sound like Im on the right track here or is there something Im missing?

[2015 Z Force 800 53/Trail EPS]

That's all a sure sign of a leaking injector. Just pull them, leave them hooked-up to fuel and power, turn the key on to pressure-up the pump. The bad one (or both) will dribble fuel. Just replace it. With 2800 miles don't bother trying to clean it/them. Also replace the fuel filter and if in CFM's wisdom decided to delete the inline filter on the Xc, put one in...a steel one made for the EFI system on at least a 4 cylinder car so there is no restriction and no safety issue. 

aight . .
Nice to have confirmation on my thought process.

Wasnt much else it could be but Im still pretty new to troubleshooting all this new fangled fuel injection stuff.

Looks like the culprit.
Rear cylinder one was WET wet, not just damp but shiny wet and the gas smell was STRONG when I pulled it.

Front one was dry and just a faint gas odor.

I turned the key and pressurized the sytem but didnt get any drips. Im guessing that it seeps when the pressure is off so maybe the spring in it got weak or something.

It seems like the right place to start, there isn't any other way gas gets TO, let alone in the engine.

My wallet is cringing already.

Also replace the fuel filter and if in CFM's wisdom decided to delete the inline filter on the Xc, put one in...a steel one made for the EFI system on at least a 4 cylinder car so there is no restriction and no safety issue. 

Like this?
https://cfmotousaparts.com/product/fuel-filter-comp-cfmoto-oem-805a-120004/
sol...

[2015 Z Force 800 53/Trail EPS]

Looks like the culprit.
Rear cylinder one was WET wet, not just damp but shiny wet and the gas smell was STRONG when I pulled it.

Front one was dry and just a faint gas odor.

I turned the key and pressurized the sytem but didnt get any drips. Im guessing that it seeps when the pressure is off so maybe the spring in it got weak or something.

It seems like the right place to start, there isn't any other way gas gets TO, let alone in the engine.

My wallet is cringing already.

Might just turn it over a couple of times to pulse it and see how it acts. Point it in a way you can see the spray. Must not leak all the time.

[2015 Z Force 800 53/Trail EPS]

Also replace the fuel filter and if in CFM's wisdom decided to delete the inline filter on the Xc, put one in...a steel one made for the EFI system on at least a 4 cylinder car so there is no restriction and no safety issue. 

Like this?
https://cfmotousaparts.com/product/fuel-filter-comp-cfmoto-oem-805a-120004/
sol...

Yeah but I wouldn't buy a CFM filter unless I absolutely had to. Not with so many better options at the auto parts store.

still do not have this all sorted. put new injectors in theyre working fine but still have some weird things.
NO CODES on my code reader.
146 psi comp on front cylinder 150 psi rear cylinder. That acceptable variance could be due to I have a fairly straight shot at running the adaptor in on the rear cylinder but not the front cylinder.

Leakdown test shows +/- 16% (well in the low/good range) on both cylinders.
And it holds steady for an extended period as well.

But my oil level seems to rise . . .
Not sure if I corrected my mileage issue yet

I don't want to run it out into the woods until I know I'm not going to blow it up . . :p

The only thing more I could do at home that I have the tools for is run a bore cam in through the plug hole . .

[2015 Z Force 800 53/Trail EPS]

Have you pulled or tested the engine speed sensor..aka CPS. I ask because although some have reported it failed more have reported it getting junk on the tip which either makes it fail to send the signal or at the right time, but multiple signals to the ECU which makes it fire injectors when they shouldn't. Just something to check as well as both valve timings.   

hhrrmmm . . Ill check the CPS.
And the valve timing is good.
Ive kept a log on that as I make adjustments or maintenance checks.

Maybe from owning an old cantankerous shovelhead my ear is pretty adept at detecting valve lash so anytime I start hearing "off" I start looking.
I had just recently varied my normal setting a little bit (.002) and didnt like the way it sounded (it was harsher sounding) and went back in and reset the valve clearances.

I roll the engine over with the covers off of course so I can visually confirm im on TDC/comp when I set the valves too. The timing marks on my Cam sprockets are paint highlighted too so theyre easy to see.

I ran my endoscope in this morning and just very light carbon buildup (almost 2900 miles). theres clear areas where you can see clear piston as well, without appearing to have detonation marking either just fairly even, light carbon build up, no dings or dents in the areas I can twist the camera around to see either. The valve recesses are clear and well defined too.

So yes, Im suspecting an electronic anomaly now.

[2015 Z Force 800 53/Trail EPS]

Lash could be OK but the timing..on one may be off. Not real likely but we are looking for something tat effects it's smooth running.

Okay. this is getting nuts.
I took it down to my dealer and they ran diagnostics all the way to starting to tear things apart on the engine.
They were communicating with CFM factory the entire time.

I removed any and all (minor) mods back to where it was before it went weird.
Ive had the RJWC header on there since about 1174 miles (at 2890) now. with ZERO issues.
Id started playing with the clutching and springs a little bit just before but my initial results there were a minor mileage drop that was well within reason. (like a 1 mpg drop)

It wasn't until I ran the injector cleaner that I experienced any issues at all.
Thats when I got the fuel in the oil, the MASSIVE mileage drop and everything else.
I wont mention the injector cleaner brand unless someone wants to provoke a holy war.

I changed out the injectors and that stopped or appears to have stopped the fuel ending up in the oil.

I removed all the clutch springs and weights and set them back to stock. (and seriously it was minor changes)

So prior, I averaged 18 - 20. mpg.

Now I am getting 4 - 4.5 mpg at best.

I have one cylinder that is a bit low on compressions tests but Above spec and my leak down tests are good.
I did a round of three tests of each on each cylinder myself and the shop did several on each as well.

My pistons are good, with no holes, or pitting or signs of overheating with minimal carbon build up and no signs of valve to piston contact (I used a bore cam) and the shop used a directional bore cam and determined that my cylinder walls are basically NEW condition.

the bike starts just fine even when its below 20 degrees. it idles fine, it idles down fine.
it still idles at the 1350 it has ever since I purchased it. (yes I know factory spec is supposed to be 1300)

It will still throw, rocks, squirrels, chipmunks and chickens halfway across the county and has never died, stalled or sputtered.

The only other thing I found (when I was cleaning it up to take it to the shop) was that the one of the two plugs on the ECM wasn't seated. (the grey side I think)

It wasn't falling out but it was even hitting the little plug ramp. so for sometime it had been riding loose.

I have a second ECM (with a tune on it) that I usually don't run and I'm going to swap it in because I know its typical average mileage as well.
My thinking being is that if it runs at the mileage I logged before perhaps my normal ECM is messed up.

The only other thing I can think of in this is if the injector cleaner somehow screwed up my fuel pump and it isnt working correctly.

But Im still new at all this E-gadget stuff.

Personally I think its a crock that a guy can get 40 to 50 mpg out of a points fired drag piped shovelhead and these tools cant get better mileage out of a bunch of computerized gadgets to begin with. . . and I dont think the mileage difference is due too "built purpose" I think its outright sloppy laziness in the power sports engineering sectors.

18-20 mpg was a good day tooling around in the woods . . 4 mpg I can barely get out of my driveway.

[2015 Z Force 800 53/Trail EPS]

And you say its still running like it used to even with this millage drop? See that's what's hard to understand. It should be running so rich it would be like running a carbed machine with the choke partly on. But it did run rich for a while with the bad injector(s) and do you still have the stock muffler on it? It has a catalytic converter that by now will be plugged up. Does this have the Evap system on it? If so a stuck-open EGR valve may...may account for some of the losses. Also, gas additive injector cleaners are known to do weird things to fuel filters and the trash they..once were holding. Hoping that was replaced before changing the injectors. Have the shop test the fuel pressure..just for GP. 

yes. NEW injectors AFTER the injector cleaner and the gassy (and really carbon fouled) oil.
I did notice today it seems to be popping more on deceleration.
I took it for a decent spin around the extended backyard.
It IS post evap . . not included or deleted in factory.

I was going to test the fuel pressure too . . gotta look at the two yard long list of tests the shop did to it.
Actually when I remember where I stuck that Ill scan it and post it . .  lol . . Ive got the whole diagnostic workup.

Ive been wondering if the cleaner could have messed up the internals of the pump itself myself.

I have a fuel pressure tester here and am just getting back to trying to figure this out this weekend.

Something is just not adding up

See if this works right.
I'm going to see what I can test out on my fuel pump pressure
and then swap in my other ECM and see if that changes anything.
Link or image is the diagnostic results from the shop.
they dont show any testing of the pump or control modules however.