Greetings. Just bought an 02. Was probably used only a few times within the 6-7 months prior to my purchase. It has 9000 miles.
Went out for a ride the other morning and discovered a very high possibility for backfiring (loud, successive popping sometimes) if the engine remained in a lower rpm state; I had to keep it in first gear untill 30mph just to keep it running continuously; That same requirement applied to the higher gears as well- Had to do 60 in 4th kinda of a thing.  Got it home, called a dude, he said spark plug. Went and bought an iridium beast for seven bucks. With the help of THIS website, I was able to experience the joy of changing a plug on these bikes; not too terrible. Changed plug, gapped to .33, sowed her back up and started it. Burst to life, which was a little abnormal considering I live in Fort Collins Co and in the morning my garage is usally in the 40’s and it usually needs a few mins of nursing the choke before it gets comfortable enough for take off. So with this new discovery..I decided to go right out and  take it around the block, quickly. It performed great, best so far even, and I took it home after about 4 mins out. Went back out in the afternoon, and after letting it warm up for 12-15 mins, I took off and couldn’t get it out of first gear it was backfiring and popping so much?? I prob could have forced it into 2nd in a burst of rpm’s…but that would have been pointless, and mean.  
Got it home, called the same dude, he said coil. Went thru some half a## testing procedures with my cousin, trying to find ohms and volts at different terminals and contacts; still not sure if we discovered anything useful. Took apart plug wire and cap…all looked ok. Screwed it back in. Sowed it back up and wanted to take it out for a min, considering it was cold, and couldn’t get it to start. Batt started to die?  I let it sit for about an hour and tried to start it again and it was just as weak. So here I am, unable to start it to further diagnosis it, don’t know if we screwed up something by taking apart the cap and wire, altho its pretty basic and we are quite able, don’t know if I have a bad coil..or if its something else.
Sorry about the escessive info, just proividing as much useful content as I can.
Any thoughts would be much appreciated.
Thanks

It's been sitting?...

Big clue there,... Did you put in fresh gas?.. Try that first...
Gonna' say it's either bad petcock, or plugged pilot jet...
Check your petcock,.. if that ain't it,.. Clean the carb jets, slide,  and passages...
How to check your petcock,...

As stated, sounds more like a fuel problem than a coil. Usually when coils start to go bad, the bike hesitates and misses...sometimes backfire. To me it sounds like a dirty carb or fuel starvation.