Motorcycle Repair: 1988 fxrs, drain plug, low rider

Question
I bought a 1988 fxrs low rider. The previous owner used ams oil. But I have been unable to make contact to find out the grade, do you have any suggestions. I need to know where the drain plug is located. And I have one last Question, where is the horn located. the previous owner took it off and I want to put it back on.Thank you

Answer
On the drain plug, it is located under the bike. It would be a hose that is clamped off at the end
Horn was located on the left side of the bike, close to the center, between the cylinders.
As to the oil, you can use AMS, I would just ask for 20W50 equivilate
Good luck and happy riding
Mike