Currently seeking some advice on a issue with my 2009 Ninja 250R

My bike only starts when the battery voltage is low and when it is just enough to turn the starter motor. I purchased a spark tester just to make sure and on a full charged battery there is no spark being produced. After running the starter to the point where the battery is heavily depleted is when a strong spark is produced. It is also to be noted that the bike charges after it runs and runs without any issues at all. The spark plugs are brand new as well as the battery. I am at a bit of a standstill because I can’t find any information regarding this issue in particular. If anyone has any ideas or tips please let me know! Thank you so much