Looks to have shaft drive - not sure what it is though. Maybe some kind of military special?? Engine is bit obscured and could be a Vtwin - maybe a Cagiva?? Bitza infâme? Mais bras oscillant de chez Guzzi, V 35 ou V 50. Can be possible a 1987 MY?
The swinging arm is from a series II V35/50/65 Moto Guzzi.