Motorcycle Repair: harley wont start, harley 883, sparkplugs

Question
I have a 2006 harley 883 sportster. It ran fine up until a couple of weeks ago it started backfiring. 2 days ago i was warming it up with the choke out for about 20 minutes and I rode up the street and back. I started it up again later and it ran but it was trying to cut out on me. I put the choke in and it cut off. After several attempts the bike wouldnt start and when it did, it would backfire. Now the battery is out. A mechanic said it may be the sparkplugs, I have the sparkplugs but the battery is still out. Can I charge the battery and use the frame as a ground? Do you think something else may be wrong? Please help

Answer
Yes, you can charge the battery in the bike and use the frame for ground. It sounds like you fouled a plug. Leaving the choke out for 20 minutes is to long. Leave the choke out just long enough to keep the bike running.
Good luck and happy riding
Mike