Ohh, I didn't know it was there! I will check it! I checked the spark plug and it is still good. The compression is way good. The mower did this nasty backfire when I tried to start it up.
I don't know if this is relevant or not, but I get the occasional huge cloud of white smoke after trying to start it many times. It looks like this engine has never been right. I don't quite understand. I will keep on checking on the things you told me to do like clean the carb and check the fuel filter.