I appreciate there’s so many variables here and I’m not even sure what question I’m asking.

When I run my heart rate is consistently very high e.g. marathon was run in 4 hours at about 85% max hr although felt pretty comfortable.

Cycling I seem to average about 70% max over a decent ride and its only big hills I get anywhere near max.

For people who are good at both sports; is this variation normal or should averages be much closer between them.

Could this indicate my running technique is poor and I should be running faster times, or am I not pushing hard enough on the bike and should be quicker?

Running is hard. Expect if you went out running 3 times a week things might change?

My HR is generally higher running than cycling.

So you are probably not far off “normal”.

You need to do an ‘on bike max HR’ test to get an accurate figure.

Mine is 189 bike 196 run

You have different max HR for different sports. A lot of it is to do with whether your body weight is supported (eg cycling) or not (eg running).