So you bought a used VN750 - now what?
SUGGESTION: Drain all fluids... oil, water, brake fluids and replace with new. Use Rotella 15/40 in the engine, an approved premix specifically for aluminum engines ( there are a number of them...see which is available to you locally), drain and look inside of the gas tank for any deposits - water-etc. Flush the Front brakes with isopropal alcohol and then refill with good DOT4 from a new jug.
After all this... make notes of how much each took. Pull plugs and air filters, clean and/or replace as needed. On the first start, listed for any obviuos noises that are REALLY wrong.... small chain and clicking may be normal. If everything checks out, stick on a helmet and get ready to head out, pump the brakes a few times to make sure they have reseated, then ease out. Put about 20 or thirty miles on, listening and noting how things act. Then bring it home and let it cool. Check the water level, oil level. Pull the plugs to see how they look... what color they are. If there was some hestitaion or uneven power, may need to clean the bowls on the carbs...( not bad idea to fit an in-line fuel filter between tank and carbs).