HR Training

Depends on what "165" is. Just an arbitrary number? A Percentage of your max HR? An upper limit of one of your training zones based on field or medical testing?

165 is 80% of my HR max calculated with the karvonen formula.  Yea I know it's not as accurate as an actual test but its all I got right now

If that's all you got, you might be better not training using HR until you can get a better idea of what your body is up to. If you are currently fairly fit, try doing a field test for AT or max HR and THEN you can have at least a ballpark idea of what 165 means.

do field tests.  simple to do, pretty sure there is one on BT, or just search google.

your HR zones will be different for the bike and run.

Yea I saw one of the field test programs here on BT, I'll try to do one this weekend atleast for the run.

With that in mind can somesone still answer the questions whether, when run training its more beneficial to make sure you stay at or right below your 80% HR max even if the only way to do that is to walk then run then walk then run etc....

It depends on what you are trying to accomplish with the training. Are you building you aerobic base, looking to runa t a specific tempo pace in preperation for a race, what? In general, running at an effort 70-80% of max HR would be considered a form of aerobic base training, although all training is ulitamtely aerobic. If 70-80% of max HR requires you to walk on occassion and you are planning on using HR as your training protocol, then yes, walk until you develop the adaptations and fitness to be running at that same effort. It will happen, not so much because of the HR, that's just a gauge, but because you are running more.