Motorcycle Repair: 1980 harley shovelhead, harley shovelhead, altenator

Question
QUESTION: I have a 1980 shovelhead , The problem is weird. When i first start the bike it runs great for a couple miles, then it just cuts out as if you turned off the run switch...it does this for a couple more times in about 5 minutes....then it runs great the rest of the day unless you turn it off for 2 or 3 hours...then it cuts out again.
I have ran a wire from the battery to the coil, replaced the coil, wires , plugs, the large main switch on the dash, put fuses along with the breakers so if any blew i would see which one died....none ever blew.
so i guess my question is could it be the battery not having enough juice to run the bike until it finally charges a little from the altenator?
The engine sounds great the hole time...never makes any funny noises and the bike runs great.
any help would be appreciated....thanks....
         joe

ANSWER: When the bike shuts off do you have power to the coil and do you have a spark?
Mike

---------- FOLLOW-UP ----------

QUESTION: it is too quik to check, soon as you hit the start button it starts right up.

Answer
It cant be the battery, if the battery was low the bike wouldnt start.
I would start by making sure you have a good gas flow to the carb. If you do then check all the wires int he ignition system to make sure you dont have a short. After that, the only other thing it could be would be the ignition.
Good luck and happy riding
Mike