Spring time here in MN, and I just changed the oil and started up my Snapper lawn tractor with a 14.5 HP Briggs model 31000. After I ran it for 3min, put it in park, then tried to put in gear again, it killed. I restarted it, then tried again and it killed. I then turned it off, tried to restart and now it turns over, but does not start. I cleaned out the air filter, but not sure what happened. This mower is about 10 years old and has been very dependable up to this point. I did leave a little gas over the winter + stabil. Also, after I tried started it for awhile, it popped loud. Thoughts?