Q- How To Install Simple Fuel Guage In Tank With Out One??

Help!! Please!!! The tank I am restoring this winter is from a
1979Honda 750K it has a simple petcock but no fuel guage. I would like
to know if it possible to get a fuel guage happening some how. I know
very little how these things work, but floats/switch or sending
units,I suppose are the norm and wondering if anyone has some ideas as
to how to get a working fuel guage onto this bike and any links would
be appreciated in advance ! The tank has a locking bar that covers the
tank cap.
Thanks
Tim C

 

I wish my bike had a fuel gauge also, although unless something really
radical appears on the market place, I'll have to do as everyone else does.

A gimballed fuel measuring device would be the best way to go. Can you
imagine a car's fuel level readings if it had to tilt regularly while being
driven (turns)? <G>

I wonder if anyone has produced a third party fuel gauge system that
utilizes a strip of plastic that is simply glued to the inside side wall of
the tank? Installation would probably cost more than the kit.

Ed Cregger

 

You could tape or glue some clear tubing to the side of the tank and then tee the ends into the
tank vent and the fuel line south of the petcock.

 

James Clark wrote:

I did see one motorcycle with that type of sight gauge. There was a
metal tube welded to the bottom of the tank and one to the top of the
tank so gasoline wouldn't pour out of the tube in a tip over.

A sight gauge like that probably wouldn't meet any DOT specifications
for flammable liquid containers though and, in case of a leak, there'd
be no way to shut the gasoline off unless the lower end was plumbed in
downstream of the petcock, as you suggested.

Several feet of gas resistant clear plastic tube could be routed up the
top side of the gas tank in the center of the tank so the highest point
of the tube was higher than the gas cap, and if there's a metal vent
tube there, hook the end of the hose to the vent tube.

If there is no vent there, continue running the hose *under the gas
tank* down to the charcoal canister so gas fumes would be stored there
when the engine wasn't running and the fumes would get sucked into the
carburetors when the engine was started.

Even with an automatic petcock, there's still a slight chance that
gasoline could be siphoned into the charcoal canister and drip out the
bottom.

 

In all my years of riding gaugeless bikes, I think I used the trip
meter for the most part, but if I forgot, and switched to reserve,
then two problems occurred:
1. I forgot I put it on reserve and run out.
2. I forgot to switch off reserve when I fill it, and run out the next
time. (Older bike, no trip meter)
A gauge, or at least a simple red light serves as a constant reminder
to fill up.. .

Now, I wonder if an add-on warning system could be built around
pressure sensor / switch connected to the fuel line with a tee
fitting. When the level gets too low, the pressure drops, and the
light turns on. No need for potentially hazaradous homebrew
electrical items inside the tank.

Low-tech alternative: From the tee, run a length of clear hose up the
side of the tank and cap it off with a plug with a tiny air hole. The
fuel level in the hose represents the level in the tank

 

The static pressure of gasoline would probably be too low for any kind
of electrical transducer.

The static head of water is 0.433 pounds per foot, the specific gravity
of gasoline is about 0.5, so you'd have less than 0.217 pounds pressure
when the tank was full (if the tank was 12 inches deep) and the
pressure would drop off to nearly nothing as the level decreased, so
the gauge will very likely be nearly useless as level dropped to where
you'd go on reserve anyway.

Barometers are really sensitive, self-contained and totally mechanical.
I wonder how a barometer movement might work measuring very samll
changes in static head.

Static head. That reminds me of Larry the Cable Guy's skit about how
his 14 year old niece got a tattoo on the back of her neck that said,
"Let go of my ears, I know what I'm doing!"

 

I don't think you'd have enough pressure difference between a full
and an empty tank to be easily measurable. Water's a little less
than 1/2 PSI per foot and gasoline'd be less.

$15-20 would set you up with a Sigma bike computer if you didn't
have a trip meter.

If you were to use an electrical resistance/float based setup
I don't think you'd need enough current to be especially hazardous,
but it'd be a PITA to set up. I guess you could also use some kind
of mechanical hookup with a float driving some kind of spiral screw
or maybe some kind of sonic measuring device.

All of these sound like a PITA. I'd go with the bicycle computer.

 

you may want to try your local tractor supply or a place that sells farm
equipment that deals in older tractor replacement parts ,the one tracter
we had when I was growing up had a very simple float guage it basically
was built into the fill cap with a tube that went into the fuel with a
simple float in it that the fuel pushed up where the tube basically went
to the cap a rod went thru the cap and into a smaller diameter tube on
top with a real soft spring around it and the spring was covered with a
small disc of metal that would start to bounce up and down when ity
started to get down about half full ,I know there has been other types
of non electrical fully mechanical guages over the years .like maybe a
consideration is a fuel guage from an old VW aircooled bug or similiar
vehicle .
good luck and good riding