I have a Honda HRX217 push mower. Backfired when trying to start it, now it won t start?!

It was running, then I shut it off to open and close a gate, and when I went to start it again there was a really loud backfire and now it won t start. It will sound like it s almost about to start but not. Then get progressively weaker each pull. I changed the spark plug and cleaned the air filter. Any ideas?

Read more: I have a Honda HRX217 push mower. Backfired when trying to start it, now it won t start?!