Fuel gauge needle moves while engine is revved....

[S4Patrick]

HELLO!

Got a 1986 Honda Aero 50 with a rather funny/ interesting fuel gauge behavior.

When I go out and ride, upon acceleration, the fuel gauge needle moves from "full" down to just above the 1/2 tank mark. When I let off, the needle heads back towards the full (F) mark. This only happen when the engine is being revved/ is climbing RPM's. I have filled up the tank completely FULL (doesn't have to be though) and this is still the case--the fuel gauge needle moves.

I have done the following:

1) Checked all fuel gauge-related wiring for any issues.
2) Changed fuel level sending unit.
3) Changed speedometer assembly (with fuel gauge needle) with a known working one.

I know that the 1985 model year can exhibit this characteristic (the 1985 has a 2-wire fuel sender unit) but have NEVER seen this on a 1986-87 Honda Aero 50. (Currently own 5 Aero 50's and I have owned at least 17)

Curious as to what you guys think/ suspect/ have experienced.

Thanks....

~Patrick

[mousewheels]

Odd problem. You've covered the sensor and wiring. I'd probably do just what you did, then check it with a meter. You sure it's not just your scooter crams all the gas to the back of the tank when you hit the throttle

Two wire sensor's resistance is low (~10 ohms) when float is in the Full position. Empty is around 95 ohms. If there is an intermittent connection anywhere, the reading will head towards empty.

-- Electrical test ideas --
You could disconnect the sensor wires, put a multimeter on it (ohms scale) and check the resistance while riding to for sure rule out the sensor.

Then re-connect, switch the meter to DC volts, and monitor each one of the leads at the fuel gauge.

[dun rite]

Hello there, It seems that every time I have a weird electrical problem it's usually a ground problem. clean underneath the screws on all the grounds?

[S4Patrick]

Hello...that's what I was thinking. Good to hear it mentioned from someone else.

As for grounding points, there's one component that I wanted to better understand. There's a metal-encased "resistor-type" electrical item that mounts to the seat lock mechanism. It's got a ONE green (ground) wire coming off of it and connects to the main wiring harness. I have never received a "proper" explanation of what that component does....Anyone car to enlighten me?

Thanks thus far~!

~Patrick

[mousewheels]

Don't know where its mounted on your Aero, but there is a single terminal resistor used in the bystarter circuit. And it uses a green wire. Fastener which mounts it ties the other end to ground.

Internally, the bystarter has a heater, the external resistance gives some adjustment over how fast and how hot the bystarter gets. In the service manual, they run a check with +12v across the bystarter yellow/green wire. Installed on your scooter, it is powered by AC, and the resistor drops the voltage and current through the bystarter.

Edit: Added diagram

Bystarter_Resistor.jpg (76.59 KiB) Viewed 2920 times