You can easily check for drive chain wear by seeing how far you can pull the chain off the rear sprocket (see picture). If you can pull the chain off more than one third of the height of the sprocket teeth than the chain is in need of replacement sooner rather than later. Keep in mind you need to replace the front and rear sprockets at the same time or you will significantly reduce the life of the new chain.
I have been involved in mechanics and motorcycling from a young age. I formed Cycle Improvements in 1981 and still have the same passion to learn today as when I started. Hope you find this blog interesting and educational.