Cycling question - Help HR training

Ok, I have just started to get back on the bike (exercise bike at the Y) since my IT band problems started 6 weeks ago.  So far I have done two 30 min workouts and felt pretty good.  However, I have noticed others on this board mention that their HR for the bike is so much lower than when they run.  I have also seen from articles that the HR for the bike using certain formula's works out to about 10 beats lower.  I do realize we are all different and without doing a max HR test I won't truely know what my max is for the run or the bike.  Now that the disclaimers are out, when I bike my HR is so much higher than when I run with the same perceived effort.  Last night (it is in my log) I used level 6 and kept my cadence at 95-100 or so and could of even gone 100-110 with little effort....HR = 148 with 75% equal to about 153 (for run).  I bumped it up to level 7 and kept my cadence at 85-95 or so with a little more effort but my HR went up to 160.  Just for fun I went to level 8 and the HR jumped to 171.  When I run I keep my HR below the 153 without too much problem on a 10 min/mile pace.    Any ideas why my bike HR is so much higher?   Is it because I am just not in 'bike' shape?  I would think outside would be a little harder and then probably a higher HR for the same speed.   What type of training should I do?  Lower my level to 5, spin at 100 and be patient until my HR stays low before moving to level 6?  Mind you that level 5/6 is about 12 mph and not going to cut it in a race 16 weeks away.  Does any of this make sense?

I will be out of the office most of the day today so any additional info anyone would need or what to help I will be glad to provide it tomorrow or later tonight.  Thanks for any input.