well charlie the bike uses a chipped ignition which means it needs a signal from a chip in the key itself to tell the immobiliser unit to spark.so you may need to check that the ariel on the front of the ignition switch has not fallen off.apart from that it can be a problem with the immobiliser unit itself,they do go wrong alot,i take it its a 50cc model and quite newish?if so you can buy a replacement cdi box without the pain in the arse immobiliser built ino it from pm tuning or electrex these companys both sell it check them out online and compare the prices. saying thet i have had a problem in the past with the circuit tracks on the back of the speedo breaking and this can also stop it sparking.really its a job for a good bike shop to sort out :)good luck
adam bike doctor
November 2006