When I got my '85 Westy, the gas gauge didn't work at all.  No movement,
no wiggle, nada.

When I dropped the tank to replace hoses and grommets I replaced the
sender, too.  The old one had worn slick where the wiper rides.

With the new sender, when I fill up completely, the gauge reads "Almost"
full and drops to 3/4 tank after about 25 miles.  The needle then slows
as it moves toward empty reaching the red area about when I need 11 or
so gallons.  Of course, I still rely heavily on the odometer, especially
when traveling.

I'd say I either have some poor connections (signal and/or ground) or
the gauge itself is faulty.  I haven't checked the voltage regulator but
the temp gauge seems to behave as it should.  Anyway, having the gas
gauge work at all is better than it was when I got it.

Mike