Ape 50 short circuit?

Hi! I installed a new starter on my Ape 50 c80 today and it worked perfectly. Until my colleague and I reassembled the flywheel and put the spark plug connector back on. While my friend was tightening the spark plug, I noticed that the light was on and turned it off (ignition was on). Then I turned the ignition off again and walked over to my friend and looked at how far he had gotten. After that, I turned the ignition back on and wondered why the light and the electric starter weren't working and it turned out that the fuse had blown. We had removed the ignition coil but the fuse still blew. Can anyone help? Thanks in advance.