If I am trying to save gas, I throw it into 5th gear whenever I'm going the same speed for a decent period of time. Yeah, a working tach does help, but you can usually tell by the sound/feel of your bike.
I'm not sure what your Nighthawk gets, but on my 79 KZ650, I can shift at 4k rpms, and cruise at whatever 5th puts me at and pull 50-55mpg.
If I ride it hard, I'll get closer to 40-45mpg.
2008 BMW K1200S
2003 Z1000 - For Sale
1979 KZ650B - Work in progress
2005 Ducati SS 1000DS - sold :'(
1994 VFR750 Interceptor - sold
1984 VF700F Interceptor - sold
2004 Hyosung GV250 - sold
Make sure your tires are inflated to the proper pressure.
Adjust primary Chain to the proper tension.
Run Syn3 oil in the engine & transmission if possible.
Change engine oil/filter every 3K ... Change tranmission oil every 5K. (depending on your bike)
Replace air filter with a K&N.
Spark Plugs: Clean and gap to proper space... replace when required.
Lean into the wind as much as possible.
Depdning on your bike shift at the lowest RPMS reccomended by your owners manual.
Don't cruise at higher RPMs.
Put NAPA(orange in color) brake pad rattle stop on the caliper pistons/brake pads(very small amount).
Change the fluid master cylinders once a year.(depending on your bike)