I currently own a 1973 Honda XL250, a 1979 Honda Mini-Trail 70 (CT-70), and a 1980 Honda Passport (C-70). I would like to hear from anyone who has experience removing the plastic leg fairing for a 1980 Passport C-70.
Ayup, I've no experience removing fairings from that particular model, but I'm pretty certain a BFO hammer would get the job done. If you want to put it back on you may want to pursue other options.
If you go to Honda Parts Nation or CMSNL (European parts outfit) and look up your model you can get a schematic for the part. It looks to me like there are 4 bolts holding it in place. I can't tell, but the air box may also be part of the puzzle. Have you obtained a service manual for the bike.
I highly recommend you invest in at least one manual for the bike. Helm published the factory shop manual for this bike (and many/most/all other Hondas). The factory manuals may leave a detail or two out assuming you're a factory mechanic but they tend to be very specific in that they usually are devoted to a particular model over a few years. Clymer makes good manuals but they often cover a range of similar bikes. The answer to your question can probably be found in either book. The Helm one sells for just under $40 and the Clymer is about the same but may be had for less. You may also be able to find a used one for less off eBay or somewhere.
I had a 1976 XL250. My mechanical learning curve made turning it into a 305 a bit of a necessity.