Let me put this gently..U R Full of... figure it out so I'm not censored!
Once ignited, our dear dino fuel burns within a few degrees of f'ng hotter than Jessica Alba. Certainly, when you're talking about temps around 1800 degrees at the exhaust valve, the only way U R going to get "deposits" is if you have over jetted the carbs...and the CVK's on the VN are notoriously lean.
And, going to the absolute minimum octane fuel will result in some pretty nasty pre-ignition if your motor still has factory CR readings. Now, if you own a beater, previously owned crap that has not been rebuilt, then 87 octane will work just fine...and most of the GY6 Chinese clones are beating your ass off the line! On the other hand, if you have a clean and tight motor (get this guys, a rebuild for a 20 something year old motor is not exceptional) then 89 octane is the minimum. If you can burn 87 octane and suffer no knocks off the line at WOT when doing a torque pull from 1500 rpms, then your motor is fubar.
As are your assumptions.
You might also want to do a little research on the octane rating methodology from when the VN750 (1986) came to life and the current watered down reality of E-15 pump gas of 2011.
It ain't apples to apples.