Chain will not tighten and causes rear wheel to not move

Loosen rear axle nuts.
Pull back on the rear wheel until the chain is tight, then move forward just a bit and tighten both sides with your hands at the same time. Try to keep the wheel centered.
Tighten the right axle nut, center the wheel and then tighten the rear.
Turn the crank slowly. The chain should have slight play at the tightest point in the crank rotation.
If the chain is too tight or too loose loosen the right nut and move the axle forward or back, tighten and retest.
When tension seems OK loosen left nut and center the wheel, then retest.

I’m happy to help further over the phone at https://www.6ya.com/expert/donald_f2ed37026a3ac881

Loosen the rear wheel nuts. Move the axle forward to loosen or backward to tighten, keeping the tire spaced equally between frame and brake. Adjust so that chain is in that "sweet spot" between binding because it's too tight and slapping against the chain guard because it's too loose.

Some models have screws in the frame at the rear axle that make this job easier. Note that it's likely that you'll need to adjust the gear shift cable after moving the axle. Good luck, and happy riding!

remove the coaster brake lever bolt. This is small bolt that holds the coaster brake lever to the left side chain stay. There will probably be a strap wrapped around the chain stay with bolt going through the strap and the lever. This usually requires a 10mm wrench (sometimes it is 8mm) for the nut and a Phillips or flat head screw driver (some times it's another 10mm bolt head).
The axle nuts are usually 15mm nuts. Loosen these (they usually don't need to be removed all the way) and push the wheel forward to put some slack in the chain. Lift the chain off the rear cog and you will be able to pull the wheel out of the drop outs.
To install, slide the wheel into the dropouts, put the chain back on the cog, pull back on the wheel and tighten the nuts finger tight. Reinstall the bolt through the coaster brake lever and then tighten the axle nuts, pull back on the wheel while tightening the nuts so the chain is tight. Then tighten up the coaster brake lever bolt. (if you tighten the axle nuts first, you won't be able to move the coaster brake lever into place to get the bolt in)

Matthew, The item giving you trouble is the rear derailler. It works by moving the chain in (closer to the spokes) and out (further away from the spokes) so that the chain can climb onto the next larger or smaller gear. Yours is apparently going too far in when you try to shift to the largest gear. There are a pair of adjusting screws that limit how far in and out the derailler will go. Use this link to find some great repair help. Just click on the derailer on the bike in the picture. Good luck.
http://www.parktool.com/blog/repair-help

hi, it sounds to me like the bike has been ridden hard and needs the chain replacing due to it strecthing. on the swing arm at the back is their two bolts sticking out the end of each swing arm their should be one in one side of the swing arm and one in the other side of the swing arm, this is right at the very back of the swing arm.
if you find these then these are the adjusters for the back wheel you then need to loosen the back wheel bolt but dont take it out then adjust these adjusters by the same amount do it in half a turn a time you need to do both the same else the back wheel wont be level keep tightening them in and this will then pull the wheel back and this will tighten the chain if its all ready adjusted fully then the chain is scrap and needs replacing, if you dont have adjusters then the chain needs replacing, it will keep coming off if its slack

you can cause damage to the bike if the chain comes off whilst riding at speed so it may be best to get the chain before you use the bike

The chain usually comes off because it is not tight enough or the chain is not aligned correctly with the sprockets. Check the chain tensioner to see if it is keeping the chain tight and not moving even though it is tight, if it loosens, replace the tensioner. Check the chain for any broken or worn spots or links, if any are found replace the chain.

On the side of the saw where the bar (what the chain goes around/rides on) where it connects to the saw there are a couple nuts. Loosen them up, push the bar back towards the saw to put slack in the chain, wrap the chair around the bar making sure the bottom of the chain is in the groove on the bar and tip of the bar, then push the bar forwards away from the saw to take out the slack in the chain. Hold it tight and tighten up the two nuts. Depending on your model of pole saw, you may have only one nut and a plastic guide that keeps it straight. Same concept though. Loosen the nut, push bar in, put chain on, pull bar out, tighten nut.
If you've ever done it on a bicycle, it's the same concept. Loosen nuts on back wheel, push tire forwards and chain gets loose. Pull it backwards and chain gets tight.

Does the rear wheel go on such that you can adjust it to take any play out of the chain? If so, turn the bike upside down or put it on a bike stand. Loosen the back wheel and pull it so that the chain is tighter and then tighten the wheel. There are other possible causes but I suspect this since you recently removed the wheel. Also I'm not sure how often the chain falls off. If this doesn't work, ask again and let us know how often its coming off. Good luck!

• Loosen off the axle nut (B) until it is only lightly tightened. Wind out the chain adjuster bolts (C) evenly on both sides until you reach the desired tension. You will see the top of the chain rise as you wind out the adjuster bolts.on pic below
  

Once you reach the correct tension, make sure both sides are evenly spaced (using the marker grooves on the adjuster blocks). Squeeze the chain against the swingarm with your hand to hold everything in place and tighten up the axle nut.Tighten up the chain adjuster lock nuts. Now you're ready to ride!

• Tighten up the chain adjuster lock nuts and thats it buddy measure the chain on the swing anr amr it should be 45mm slack on the swing and arm where the chain slider is
  

No.That was the problem.The chain and the sprockets needed to be renewed.
When you will take, the rear sprocket's base, off the axle check it's bearing.Just put your finger in and turn it slowly to see if it "locks" instantly.It will be nice if you renew it now that you disassembling the chain drive system.