Cleaning and lubricating Plain roller chain
Remove and place the chain inside a large (4 litre) disposable plastic oil jug. Add kerosene or your favourite cleaning fluid. Close the container, agitate and then drain off the dirty solvent, repeat process if necessary until the chain is clean inside and out.
Now pour thick gear oil into the oil container along with your chain. (inexpensive chainsaw bar oil works dandy and is available in a variety of weights) Shake and then leave it set until lubricant has completely penetrated into the rollers and pins of the chain.
Hang the chain on a hook over a catch pan until all the excess oil has run off, wipe the chain lightly and re-install on your bike.
Ride motorcycle vigorously and repeat
Unsure how much your chain is bagged out, then lay or hang it next to a length of new chain, if it's stretched out by one link over the length of ~100 link chain then your chain is stretched by 1% and on the way to needing replacement soon if you want your sprockets to last.