Motorcycle Repair: 88 Yamaha 250, couple nights, carburator

Question
How's it going?  I've got a 1988 Yamaha Route 66 (250). A couple nights ago, I was stopped at a red light when it just quit.  It was running great up until then, idling normally and everything.  I hit the start button a couple times with no luck.  After I got it off the road I tried to push start it because the battery was plum dead, everything was dimmed out.  This battery is only a few weeks old.  After push starting it it ran for a few seconds, sputtered, backfired and died.  The gas tank was full, I tried switching to reserve also.  I push started it a couple times with no better luck.  I just got it out of the shop the other day having a jet replaced in the carburator because it was dumping too much fuel and fouling out the plugs every couple weeks.  This in mind, I still had an extra set of plugs in my bag so I changed them out and push started again.  Still the same thing.  A couple times I got it to run for a minute and tried to ride it in the parking lot to keep it going but as soon as I would change to 2nd gear it would die immediately.  I finally had to call someone to give me a ride and haul the bike home.
Like I say the battery was new, I checked all my connections, cables, fuses, and the whole works.  Any ideas?  Could it be the alternator (or generator, please forgive my ignorance) Would this have anything to do with it running rough and backfireing after I got it started?  Up until this point is has ran great, I've rode it a few times after I got it out of the shop the other day with no problem whatsoever.  It just quit with no warning whatsoever.  I'd sure appreciate any advice you have for me.  Thanx a lot, and have a nice day.
-Rodney Manning

Answer
Hi Rodney.

This sounds like a probable charging issue.  But to be sure, you need to check a few things.

1)  Charge the battery.

2)  Check the plugs that you just replaced and see what they look like. See if they look normal or fouled.

3)  With the battery charged, start the bike and see what the voltage is at the battery terminals while it is running.  It should be charging at 14 - 16 VDC.  If it is charging at less than that, then your stator coil has failed.  If the bike is near, at or beyond 50,000 miles, then the problem is  extremely likely to be the stator coil.

Let me know what you find.

Good luck and ride safe.
FALCON