The chain as jumped out the teeth how do you put the chain back?

if that is the gear you do a lot of time in then maybe the teeth of the cog are worn and the pitch for the chain is now not correct causing the chain to tend to ride up on the teeth and then jump back into place causing the gritty feeling

your timing chain/belt has jumped teeth get it fixed before you blow it totally

2 questions come to mind has the new sprocket got the same pitch ( distance between teeth ) as the crank shaft sprocket as this will make the chain jump out after a few degrees of movement. A quick check is to wrap the chain around the sprocket and see if there are links that do not sit fully around the teeth. There are different pitches for teeth and chains ( BA-- AM and metric)

That knocking noise could be that the teeth on your main drive are worn out and chain is jumping them on acceleration.Pull th primary cover and check the drive gear for chain on motor sprocket.Replace it if worn to that point.

Look for some Youtube videos on this repair. If I remember correctly the links on this chain have different color metal for the spots that the cam tooth goes against. When each side is in the proper tooth the right and left colored links will be on the cam mark and the crank mark should be on the timing TDC mark. Sounds like the slack you describe is wrong and a tooth is off because the tensioner is allowing slack.. You need to slip a tooth one way or the other until the tensioner has room to be in a neutral position.

Sounds like your timing chain has jumped out of time, if the timing chain is old, the chain jump a few teeth putting it out of time having it fire at the wrong time when the exhaust valve is open. Check timing by pulling #1 plug - bring #1 piston to the top and line up timing mark , Ifind it easy to put thumb over spark plug hole and have someone bump the engine over and feel the pressure relief stop before you feel vacumm - timing mark should line up if the timing hasn't jumped

Not common unless the car has not been maintained. Without regular oil changes, the chain eventually stretches, the sprockets wear, and then the chain may jump a tooth. It is more common with overhead cams, because the chains are much longer and rely on tensioners that wear out.

Sounds like your chain is stretched and not fitting the sprocket properly or is just too loose. Check your front and rear chain sprockets for wear and ensure the teeth are straight. Check to insure the chain fits snuggly on the rear sprocket. As a chain stretches over its life, it won't fit in all of the teeth on the rear sprocket. This will cause the chain to ride up on the teeth at higher RPMs and jump (causing the feeling of a jolt or **** as it grabs again). Typically, the chain should have no more than an inch or so of play when properly adjusted.

Rear set teeth may be worn / chain worn and jumps (the bearings-spacers loosen in chain links) / or if you have put new chain make sure its the same length.

Hi there. Sounds like the chain jumped a couple of teeth putting the valve timing out. Check timing marks on crank and cam. Check for slop in chain. If sloppy, replace.
Thanks
Paul