So I got the motor from Amazon, " 10mm Flat Shaft Central Door Lock Actuator Motor FC-280PC-22125 FLAT SHAFT, D Spindle, Power Locking Repair Engine ". BUT, here is what I should have ordered, " 10mm BRASS COLLAR SHAFT FC-280PT-22125 Central Door Lock Actuator Motor, BRASS COLLAR SHAFT, Power Locking Repair Engine Replaces Mabuch ". More on that in a minute.
I also ordered the JB Weld gasket compound, Black.
My order total was about $15. the order came in yesterday.

I did the repair like this.
removed the air box
removed the left side wheel well plastic
turn the handle bars to the right fully
from the left side wheel well, the actuator is reachable.
10mm socket with 3" extension, 1/4" drive. (smaller so I can get my giant sausage fingers in there)
there are 3 bolts that remove the actuator from the differential and 4 bolts that secure the actuator cover.
remove the bolts that hold the actuator to the diff, NOT THE COVER.
the wire (cable) runs up the vertical frame rail to a white round connector located just under the gear selector. unplug that.
there are 4 zip-ties holding that cable to the frame rail, cut those and free the cable first , then wiggle the actuator away from the diff. you may have to use a flat-head screwdriver to help free the actuator, but mine came off by hand.
take the actuator to a work bench or clean area and remove the 4 bolts that hold the cover on.
remove the cover, do you smell that? mine stunk to high heaven of burnt electronics.
there is that little motor that I am talking about, 2 Philips screws are holding down a brace, remove and then free the motor away from its spot. careful, don't jostle the rest of the gears and such out of their spot.
the wires that go into the motor just pull straight out. the connection is just a little brass tab that slips into the motor.
blue wire and a yellow wire.
take a look at the motor, its probably easy to tell that its burnt up, and did I mention the smell. (LOL)
take the NEW motor and place those brass connections exactly the way they came out of the old motor. its easy to get it right, the wire lengths are such that it only fits well , the correct way.

that first motor part number that I listed, the one I got, does not have the brass collar on the shaft. the brass collar is flat on 2 sides and I had to pry the collar off of the old motor and place it on the motor that I bought.
save yourself the trouble and get the correct motor.

put the new motor back into the spot that the old one came from. the shaft goes into a white nylon drive screw.
once it is seated, replace the strap that holds it down and put the screws back in.
next, I put the front plate back on and reconnected the round white plug.
I tuned the key on and pressed the 4WD button. I could hear the motor run and I could see the actuator turn on the back side.
I flipped up the diff lock switch, boom, more movement. feeling good!!
OK, I took the actuator back to the bench, removed the cover and applied the RTV gasket compound pretty liberally around the area where the cover sits.
back together and tightened the cover back on. excess RTV squirted out and now my hands are black and those sausages look burnt.
back to the bike
placed the actuator back on the diff, you may have to wiggle a bit to get it to fit flush, but it will go back on.
I put all three bolts back in and tightened by hand. the tiny 1/4" ratchet finished the job.
I think there is a torque spec here, not sure. But I think I over tightened the actuator and it did not want to move freely. I backed off a 1/4 turn (still tight) and everything seemed to play well together.
replaced the zip ties, reconnected the round white connector.
put the wheel well plastic back on, put the air box back on, buttoned everything up.
now the test.
sitting there, the actuator wasn't acting just right. I got that sinking feeling....
so I cranked the bike and put it in gear. brake is still on. I rocked the bike forward and back.
that got everything to work.
I took the bike for a test ride and the 4WD worked perfectly. I switched in and out of 4WD at various (low) speeds. I applied the diff lock in high and low gear.
I think I fixed it. I went for a ride on some local trails and tested the 4WD several times, no problems.
I think I fixed my 4WD, and for $15 instead of the $500 replace.
I will continue to test it, if it breaks again, I will post it here, but for now, I am feeling pretty good about the repair.