This happened to someone recently

[Wirenut]

Yeah, it sounds unbelievable, but since I never owned one, I didn't have to deal w/that. It may have been the headlight, but about that I'm not sure.

I did like the single-cyl Ducatis though, the 250/350/450 series was known for their stout, reliable engines, the electrical systems, no.

Not to hijack the thread but didn't they have positive ground systems as well?

 

[Miles Long]

When i look the circuit board, the bulb is serial connected with the relay (Green wire).
All we have to know is :

-Does the current come from the Relay, goes in the green wire and finally in the thermistor. If yes a toasted bulb doesn't change anything.
-Does the current come from the bulb, goes int the green wire toward the relay. If yes a toasted bulb keeps the pump running.[/QUOTE

Thanks for the input, Thor -
What do you mean by "a toasted bulb doesn't change anything"?
The way the system should work is.....in my opinion.....
The fuel light bulb should light up during the pre-ride testing phase (see previous posts)
The fuel light should light up when the sender senses a low fuel condition - the same sender/relay will shut off the power to the fuel pump. Stumbling of the motor is not immediate, due to the remaining gas in the carbs.
Activating the reserve position of the fuel switch sends voltage from another source to the pump, running it until the tank is dry. The fuel light stays on the entire time.
A toasted bulb should not prevent the pump from running in the reserve position, stranding a rider. An operable bulb is only there as a warning of low fuel, and a reminder to switch to the reserve position.
I certainly will be doing tests on my bike's system, next time I have the fairing off. The fuel bulb is much harder to access than when in the oem console. Until then, I will make sure it lights up during the pre-ride test, and also let the bike warm up with the switch in the reserve position.
Cheers!

 

[D-Max2012]

and also let the bike warm up with the switch in the reserve position

Miles, I have to ask,, what's the reason for this??

 

[thor_eyerdhal]

A toasted bulb should not prevent the pump from running in the reserve position, stranding a rider. An operable bulb is only there as a warning of low fuel, and a reminder to switch to the reserve position.

I am agree, it should be like this.

But i remember discussions with french members of the club, some of them were the victims of the toasted bulb, the pump keeped working until tank was totally empty...

We have to know if the current from the bulb only goes thru the thermistor to the ground or if it triggers the relay too. The schematic doesn't show the polarity of this small part or circuitry.

 

[Miles Long]

Miles, I have to ask,, what's the reason for this??

To insure that the power feeding the reserve switch is actually working.
Best to find out in the garage, rather than some where on the road, seeing the low fuel light, switching to reserve, and not having the pump work.
This is all based on how I understand the way that the fuel system works. Maybe I'm wrong.
Maybe the old school manual reserve valve was the way to go. No circuits or bulbs to worry about. Old tech is best!
Gotta go. Gotta flip sides on the vinyl in my record player........:biglaugh:
Cheers!

 

[D-Max2012]

Had a chance to test the bike today..
I Let her idle while siphoning out fuel.
Brought the fuel down to were I could see the fuel sender was no longer submerged.
I did not see the low fuel light come on.. I kept it running for a while..
I tapped lightly on the relay, then I could see a faint glow of the low fuel light..
The glow slowly got brighter and brighter BUT, while it was getting there, the pump was still pulsing fuel. I have a glass filter and it looked like a steady heart beat.
When the light got bright red (still too dim to see in the sunlight), I noticed the pump lost its pulse. Let it run for a while. I flipped the RES on, and the pump surged and leveled off to pulsing again. So it looks like the system is working.

I let the bike run till it shut off, flipped it to RES and let the bowl re-fill. Started right up again. Here's the strange thing.. Looking into the tank, the fuel level was almost drained.. Maybe 3mm of fuel left in the tank. The fuel sender is now out of the fuel about 3.5 inches..

3mm of fuel will not get me very far to the next station..
I thought the system should kick in, just after the sender is no longer submerged in fuel.

I wonder, whats the symptoms of a failing relay, vs the symptoms of the failing fuel sender??

 

[Miles Long]

checks out dis video, from a good ole' Newfoundland bye....
https://www.google.ca/url?sa=t&rct=...xkUtU4&usg=AFQjCNGwq0zcZ6BohiCCx00x-MWDLRsO4g

Sure sounds like your thermister is nor working as it should. Apparently, they just break down with time. Another site on the internet said the increasing amount of alcohol in gasoline contributes to early failures.
My bike will begin missing only a few kilometers after the light goes to it's brightest, and stays on continually. After switching to reserve, I have gone as far as 50 kilometers before filling up.
As previously stated, I can see the low fuel light very clearly, even in bright sunlight, consequently I get a good indication of it's operational characteristics, which are very consistent.
The light will begin as a very dim flicker, then goes out for a time, then begin flickering more often, all based on how flat the roadway is. Hilly terrain causes much more flickering, at dim (but gradually increasing) levels of brightness.
Eventually the light stays on all the time, at it's brightest. A few k's later, the pump begins to cut out.
One quick and easy thing you could do, as a test of the sender/relay -
Make up a LED bulb holder, with a shroud, similar to a shift light arrangement.
Mount this next to your speedo, using whatever works for ya ( ducttape?)
Pick out a 12 volt (nominal) LED bulb that has a wide range of acceptable voltage for operation. The ones that I use as warning lights for auxiliary circuits will operate in the 4-14 volt range.
Because the thermister obviously send out a low voltage signal as it begins to heat up due to lack of gasoline, the LED bulb should respond quicker than the incandescent OEM bulb.
This should give you a better indication of the true reserve range of fuel in your tank. If it works, you may want to make the bulb and holder a permanent installation.
Cheers!

 

[Specs95t]

Last weekend, I was riding two up with my wife and started to get a full power loss and bucking situation with the bike. We were headed up a pretty good hill with the sun on our backs.

Flipped over to reserve and the power surged back. Looked down at the low fuel light - and after some squinting and concentration, saw that the light was on...

Point is that the light is dim - even when fully lit up - especially if the sun is on your back.

I get to 90+ miles on the tank if commuting solo and riding normally, with normal cruise in 5th gear.

We ran out of fuel with high 70+ miles on the odometer because I had gone for a fun ride holding higher RPM and then finished the tank with two up riding...

Good datapoints...


Sent from my iPhone using Tapatalk

 

[Miles Long]

Last weekend, I was riding two up with my wife and started to get a full power loss and bucking situation with the bike. We were headed up a pretty good hill with the sun on our backs.

Flipped over to reserve and the power surged back. Looked down at the low fuel light - and after some squinting and concentration, saw that the light was on...

Point is that the light is dim - even when fully lit up - especially if the sun is on your back.

That whole tank-mounted console thingee was a bad design, so an automotive-style dash was one of my first mods. Much better to view the lights, and keeps your eyes on the road.
Cheers!

 

[D-Max2012]

That's some good info on that thermister and mounting an LED.

That's a cool looking dash Miles.. Reminds me of a Harley.. I'd bet the low fuel light is way more visible.

I'm questioning the symptoms of a failing Relay vs a failing fuel sender.

If a fuel sender is starting to act up, will it not sense the hot or cool situation not activate the circuit when its supposed too? or not activate at all?

When it comes to relays,, I've see many of them start acting up, over time, just from carbon buildup from arching. It could have been coincidence that after I tapped the relay, I noticed a very dim low fuel light..

I just keep thinking that I should have started to see the lamp glow, not long after the head of the sender was no longer submerged.. What's your take on that?

 

[Miles Long]

That's some good info on that thermister and mounting an LED.


I just keep thinking that I should have started to see the lamp glow, not long after the head of the sender was no longer submerged.. What's your take on that?

Why not do a bench test, using a spare battery, and a container with gasoline? Similar to testing a temperature sender, but easier - no water to heat up, or thermometers to watch. Use the original bulb, see if it works, then instead of the bulb, measure the increasing voltage, as the sender is gradually taken out of the gas. Would give you an idea about which LED bulb to use.
As you noticed in the video, the thermister is located in the middle of the tube. I don't know if the Yamaha ones are the same, but this might determine when they start to react with the dropping fuel level.
Didn't you say that you have a spare sender? You could try this one first.
Detailed fuel pump relay testing is covered in the Clymer manual, page 242. Let me know if you haven't got this info.

 

[D-Max2012]

Had a chance to test a spare fuel sender.. The readings were about 2k ohms more than book recommends.. It was cracked on the side of the housing, which is not a big deal, since there are holes in the sensor case anyway. I found a video of a guy fixing his Honda Magna fuel sender

https://www.youtube.com/watch?v=gjREKxkUtU4

by buying a $3.00 thermistor and replacing the old one. I decided to try it, since I had a damaged sender anyway. The new thermistor read perfectly as per the Yamaha specs.. So, after soldering the new thermistor to the housing,, I went outside and powered up the bike. While running, I siphoned out the fuel. After the head of the stock sender was no longer submerged, I watched how long it took for the red light to come on, and pump to stop. It took almost 9 minutes for my sender to warm up enough to get a faint glow out of the bulb. By this time, there was only about 3mm of fuel in the bottom of the tank. So, it looks like the relay is working, because if it wasn't, it would not work no matter what sender I tested.

I created an extension cable to attach to the test sender, to the mating end, inside the bike. Then I put the test sender into a glass of gasoline. After giving the bike some gas to run this test, I started back up the bike.

This time, I pulled the sender out of the gas and watched the operation. This time it took about 1.5 minutes, before I started to see the red glow. By 2 minutes time, the red light was bright and the fuel pump had stopped.

So it looks like, over time, the fuel messes up the thermistor, causing it to become desensitized to temperature changes. I need to take a pic of the old thermistor.. It looked corroded..

 

[Miles Long]

Great info!
I remember reading something on the internet, while searching for that first video, about how ethanol-laced gasoline is hard on the thermisters. Or maybe it was in the video.....
So a three dollar part may be the key to reviving a lot of wonky low fuel indicators!
That is, as long as the owners have the patience to fix them.
Maybe we can expect a How-To video, specific to V-max sender repair????
Cheers!unk:

 

[D-Max2012]

Maybe we can expect a How-To video, specific to V-max sender repair????

I can create one.. Of course, the person dong it would have to be comfortable with soldering, and, how the fuel sender looks, after completed..

In order to get to the old thermister, you have to split the canister open.. The old one had a crack already, I used a Dremel tool to add two more splits down the side of the body. i had to pry it open to get the old one out. Not really complicated. It's just time consuming.

Take a look at the test housing and the other parts I had to mod to do the testing.


So now that I know what to expect, I could actually do this, making it look way neater than the test sender.

 

[D-Max2012]

Just posted a couple of videos on my testing....
1) https://www.youtube.com/watch?v=cMNo4EaCfKY&feature=youtu.be

2) https://www.youtube.com/watch?v=qTU_WDld--U&feature=youtu.be

 

[Miles Long]

Thanks for posting those vids. You obviously have a lot of patience, and like to find the root causes of problems.
So, now that you have a working fuel sender, are you planning to improve the visibility? Lots of possibilities here!
- a brighter/larger lightbulb in the console.
- relocate the above.
- run the signal from the sender thru a step-up relay, to trigger a audio signal, as well as a light.
- run the signal to a flasher relay, then to a light.
Can anyone think of something else?
Of course, a working low fuel indication is useless, if the aux. power to the fuel pump doesn't work. Test it before starting a day's riding, folks.
Cheers!

 

[D-Max2012]

Thanks Miles,,
1) I want to make a device to plug directly into the bulbs housing for power and fitment.
2) It must replicate the same load that the stock bulb does. I want the low warning system to think the bulb is still there.
3) I want Hi Output flashing LED coupled with a Hi dB piezo buzzer. (any non standard sound will draw your attention to look down).
4) it must be waterproof.

That's all I can think of right now..
Now I have to start looking into finding the parts.
I figured, I can do a clay molding of the bulb housing, to get started on the shape and fitment.