If caught working in Beijing without a work visa, you will be fined a paltry 500/1000 RMB! But you must leave the country within 10 days or so. However, you needn't go back to your country of origin to obtain your new L visa before returning. You can go to a 3rd party country on China's borders. A Chinese visa office in that country can issue you a new single-entry Chinese L visa. Kill two birds with one stone by vacationing there - call it a working holiday, working on getting your new Chinese visa...LOL! After that, return to China. Been there, dunnit! Compared to the visa violation penalties in other countries, China's penalties are very very reasonable if you have some cash. Then you can buy yourself out of trouble relatively cheaply. But in contrast, if you're unable to do so, you'll be put behind bars! That doesn't bear thinking about!