The ohm range of the meter is in the manual... can't remember what the values are though.
Mine is shot. Took it out and one look at it told me it's the unit itself and not the wiring. It didn't even have a float on it anymore lol.
Even without the ohm range from the manual you can just take it out and look at it and if everything looks fine, just test it and it should give you a smooth increase/decrease in resistance.
There's a downloadable manual on here, I just don't have the link.
Also, yes, that's what reserve is there for... so you don't run out of fuel. Put it on "on" and when the bike starts acting like it's out of gas, pull to the side, put it on "res" and head to the nearest gas station, then switch it back to "on"after the fill up. Easy.
1985 VN700 unknown mileage (over 33K)
Iridium spark plugs
NGK wires and caps