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G400C Questions/Comments

Posted: Sun Aug 02, 2020 3:44 pm
by DrScoot
I want to start a thread regarding specifics to owning a 400 since there are very few owners on this forum. This would be comments/questions in regards to the actual operations/maintenance of the bike. I will start off here for any owners. Have you figured out how the fuel light works?

On my bike, the fuel tank indicator light comes on around 150 miles of usage from a full tank. However, when you look in the tank there is still plenty of fuel leftover. Additionally, the actual indicator light is pretty weak in this state, suggesting that it may increase in brightness the lower the fuel gets. The manual just states that the light will come on and no mention of a dim value for tank levels.

I have been hesitant to run this to the end to test out this theory during my work commute but one thing is for certain, when you turn the bike on, the indicator does go to full brightness before settling at an off or lower brightness value.

Has anyone else noticed this? I'm going to try to run it lower to see if there is a change in brightness and will update once the study is complete. Is this a common effect on other bikes/equipment to even be plausible?

Posted: Sun Aug 02, 2020 8:34 pm
by eggsalad
Just thinking out loud here... The fuel level sender is probably a resistance unit with a float, just like the scooters. The more the float drops, the lower the resistance gets. Then I'm betting they put another resistor inline with the indicator light.

So when the tank is full, the overall resistance is too high to pass any current at all to the light. As the fuel level (and the float) drops lower current begins to pass through to the light, lighting it dimly - perhaps too dimly to see in daylight. And the lower the resistance gets as you use up fuel, the brighter the light gets.

But that's all just theory. I really have no idea how your bike is actually built.

Posted: Mon Aug 03, 2020 2:56 am
by DrScoot
Yeah that's kind of what I am suspecting as its very dim in normal lighting as compared to other indicators. However, given there is no mention in the manual for that type of operation I found it questionable. The light tends to come on to a somewhat dim level maybe at 0.5gal remaining or more (hard to tell). I get queezy as I am using it mostly for commuting so don't want to run out of gas en route to work so I usually fill it up around the 200 mile mark and check and theres probably a good half a gallon or so left so not sure if the light will get brighter once that drops or if the light just sucks lol.

Also wasn't sure if that was a similar feature on other bikes, etc.

Posted: Mon Aug 03, 2020 4:00 am
by eggsalad
yes, you will need to find time to take a casual (ie, not commuting) ride with a pint of gas in a bottle in your backpack. That's the way to find out for sure.

Posted: Mon Aug 03, 2020 1:06 pm
by tenders
Not sure there is any precedent for a variable-brightness fuel idiot light. Or any idiot light, for that matter. The fuel lights on my machinery might flash a few times as the level sloshes around at the trigger point, but that’s it.

Posted: Mon Aug 03, 2020 9:09 pm
by eggsalad
I was just bored enough to dig into this. Couldn't find a G400C wiring diagram nor service manual, but I found one for the Shineray XY400. Shineray is the company that manufactures the G400C for Genuine.

Turns out I was pretty much spot on. The fuel level sender is indeed a variable resistance float-type sender. Probably an off-the-shelf part from some vendor. The indicator light is an LED.

An LED will indeed increase brightness until the full forward voltage is achieved.

And tenders, there might not be a precedent for a system like this, but it does make sense in light of trying to build a motorcycle "low fuel" light as cheaply as possible.

Posted: Thu Aug 06, 2020 2:07 am
by DrScoot
Nice! I might try the ol pint of glass trick but I definitely need to look at that wiring diagram. I absolutely overlooked that. That's a good catch right there. So from what you have seen it does look like a variable brightness indicator? Seems odd they wouldn't mention it; although, trying to decipher a correlation between a brightness value and the level of gas might be a challenge. If there is a signal, it might be interesting to wire up a circuit to a display or something just for kicks.

Posted: Thu Aug 06, 2020 7:42 am
by eggsalad
DrScoot wrote: If there is a signal, it might be interesting to wire up a circuit to a display or something just for kicks.
You could wire it up to... I dunno... a gas gauge?

Posted: Fri Aug 07, 2020 3:34 am
by DrScoot
Now that'd be something!

Re: G400C Questions/Comments

Posted: Mon May 24, 2021 2:16 am
by DrScoot
Just bumping in here to post some of my studies. I have not run this baby down to nothing yet, but that is still on my list. However, it does appear that the light does not change brightness. It is just very dim, or a poor color for use in daylight. At night its very clearly visible, its just during the day it is very hard to see. I suspect its no more advanced than a simple turn on once the fuel reaches a certain level. Id be curious if it is dim for any other riders out there as well or if I just got a sad LED in mine. Cheers!

Re: G400C Questions/Comments

Posted: Fri Jun 02, 2023 11:46 pm
by Frobig
The white gauge faces are the culprit. My G400C is the only white-clocked bike I've had, and I don't like that about it. The idiot lights are almost invisible in the daytime and I can't read the numbers at night. I do think the gas light is on/off. Meanwhile, does anybody know how to change the speedo or tach light?