Sounds like it could be an ignition problem - check the coils for cracks (although that is often a damp weather problem) and make sure there is good contact between the ignition control unit and the mount which acts as a heat sink (use radio shack heat sink compound).
On the old /2s this symptom meant internal shorts in the magneto coil.
cad jim, your bike originally (and probably still has) a points ignition system. Most of drewboid's comments are regarding the models after 1980 that have electronic ignition.
The coils on your bike were not prone to cracking like the later ones.
You do not have an ignition control unit, so you don't need any heat sink paste.
I am not much of an expert at troubleshooting, but I would take a good look at your points, and possibly the condenser (you can't do much with that, except replace it). Make sure your timing is correct.
To give yourself a baseline,
replace your spark plugs, caps, and wires. If your coils are original (black, with a yellow Bosch sticker on them), you might consider replacing them just because they are getting pretty old. While you are there, check out the
front coil mount. This WILL BREAK at some point in the bike's life, taking the MAIN GROUND wire with it.
Some people have reported the rear mount breaking, as well, but mine is still holding.
I once had a /2 that would start right up when cold, but never when hot. This was pre-internet, and I didn't know much (and neither, aparently did my dealer...). I later found out that a bad coil would cause these symptoms.
Granted, a /2 is a TOTALLY different animal, but the basics are the same.
Topic: 79 R65 Hard Starting After Engine Warmed Up? (Read 1295 times)