Yamaha Virago Low Fuel Level Sensor Repair

[@livinglikarockstar]

Great detailed video, pointed to the correct solution which is damaged thermistor. Previous wally owner attempted rusty tank repair left the sensor and cap on rather than taping the holes. tank seal appears to have slightly coated the thermistor keeping it from heating up to trip the light. Sealant was flaking off inside the tank as well in large chunks. Ended up taking both tanks to professionals for boiling and correctly sealed, luckily there's one local shop. Only a few left in my area as plastic replaceable radiators are all the norm put all but just a few shops out of business. Was about to order a potentiometer for circuit test then figured simply complete the circuit momentarily with a very small strand wire, low fuel light should illuminate which it did! Off to thermistor repair land, thanks much!

[@KensWorldRestorations]

That's great news that you were able to get to the bottom of it since it sounds to me like you had a far worse experience than I did. I'm not a fan of coating the inside of the tanks for the reasons that you mentioned. The whole idea isn't a great design but it's cheap and served the purpose of alerting the rider of low fuel. A fuel gauge would have been nice...

[@johnczirjak]

A very detailed video on the fuel sensor. I learned a lot about this little unit and appreciate all of the research that you explain in this video. Very well done! I now know what to do if my own sensor (XV1100 is the same) doesn’t work and how to test it as well. You even made a video testing it on the road! I really appreciate the work you put into this and I look forward to your future Virago videos. Thanks

[@KensWorldRestorations]

Thanks John!! I was afraid my videos were too technical - old habits die hard. Hopefully I didn't put you to sleep. I've got a lot of work done in the past 6 months and I still have about 5 hours of raw video to chew through from when I did the front brakes (turned out to be a total nightmare). Anyway, thanks for the kind words, I've got a lot of work to do and I hope to be documenting all of it, including the total tear down and restoration and the road trips/travel blog as well.

[@deankay4434]

As a certified ASE Master Tech since 78, auto's also use low fuel sensors & a light. I worked at a Yamaha dealer with another tech who quit after a week of my employ. These are NTC thermistors 1k ohms at 1/8th watt. They never get hot enough to start a fire as many have asked. First, no or little oxygen. Many schematics show the ground (either end) but goes to the cluster or gauge into "Logic". These operate an LED depending on color require a resistor about 460 ohms in series with the LED. Remember, the thermistor goes to zero ohms when dry or no fuel. This allows a full B+ to enter the LED and it will burn out. If adding one to a cycle or auto that doesn't have one, keep the correct resistor in line (Call in series) and tin the holder and can as you can only hurt "SMD" components called surface mounted devices. Those with wire leads are not at risk of damage during soldering. Also, if a home improvement store is near by, go purchase dielectric grease now made by Permatex. It is next to epoxy and mirror adhesive. It keeps moisture out of connectors during rain, washing or dew with night low temps with moisture or humidity is high. The can is easy to make if you have any tin can headed to trash. Just solder the outside as the inside is sprayed with a lacquer or food grade enamel, depending on contents. Tin snip and bend around a socket in a vise. Allow for room on bottom to pie cut, fold and solder drilling some holes for fuel. If anything, place some wax paper or parchment paper. Both are insulators and soak in gas over winter did nothing to affect its condition (Optional) as it keeps the thermistor wire from touching can on bottom half. A salvaged printed circuit board cleaned on a wire wheel is fiberglass. Few plastics make the long term gas test. Just drill a hole in the middle, place a dab of solder on the under side of cap, cut the can with 3-4 tabs and bend over to hold. On its side, dab solder on top the add pre-tinned wire to complete the connection. With a hole on top of sender unit, add epoxy or 3M panel adhesive. Body shops use it everyday almost. Talk to a tech and tell them what you are doing and perhaps leave it with them for a day or two. Ask them what 12 pack of beer they want. You will get a long way and have an LED low fuel light. ASE Master Tech since 78, retired.

Tengo una Virago 750 del 1992 y no andaba el sensor de combustible. Acabo de repara de la misma manera y me resultó. Bravísimo !!!!! Very Good!!👋👋

[@Quocle603]

Great video. You really broke it down to help us out.

[@paulchambre6771]

I replaced mine ('89 XV750) with an NTE 1K NTC thermistor. And the light does come on at low fuel now, but the light is not bright enough to be noticeable in the daytime. At night it's fine. I am planning to add a circuit to switch on the light with a transistor when the thermistor resistance drops, so it will be as bright when on for low fuel as it is when cranking.

[@KensWorldRestorations]

That's genius level stuff. If the light is not bright enough as it is, then it sounds like the fuel control relay isn't supplying enough current to the bulb (or make sure the light bulb itself is the proper rating). Double check the connection at the fuel control relay and check the lamp socket - there may be some corrosion at either end. Otherwise, the transistor/switch is a really good idea!

[@roybm3124]

Amazing video very well explained.

[@KensWorldRestorations]

Thanks! Really appreciate the nice comments!

[@HypnoticAbyss]

Feels super odd to me having something that gets hot inside the gas tank. Be I have the same issue and need to repair mine. Great informative video!

[@KensWorldRestorations]

I laughed when I read your comment - I thought the same exact thing. I was sure it would have been a capacitive probe or something like that. So the OEM thermistor is only 1/8th of a watt but it still heats up to about 70C when in free air. Made me nervous too, after looking up the flash point for gasoline which is -45C. Then I realized it's the ignition point we need to be concerned with and that is 232C so we're safe. But you're right, a weird way to do it - stick a hot electrical device in the fuel tank to measure a low fuel condition.

[@JM-rw9je]

Japanese badass engineering 👹

[@7sj3Ax]

Very useful video !!!

[@KensWorldRestorations]

Thank you! I know it's a long one but there was a lot of mystery to uncover. Thanks for watching!

[@JAKWEES]

The sensor on my project 85 xv1000 is epoxied on for some reason. leaks pretty bad. Should be fun dealing with that

[@robhack5265]

It was very useful for me. Thank. A new sensor cost o ver $120

[@KensWorldRestorations]

Hey Rob...that's absolutely criminal to charge that much. If you're ok with soldering or have someone who can help, you can buy the thermistor in the can from Aliexpress in China. They are $10 each and they ship by mail so it takes a while but it's worth the wait. Here's the link: www.aliexpress.com/item/32872117309.html

[@kevinruddy448]

Is there a petrol reserve on my 535cc Yamaha virago motorcycle 🏍️⛽🤔🇬🇧

[@AlyciaCarbonaro]

Is there a way to get a new bracket instead of the entire sender? My parts work but the metal bracket corroded.

[@KensWorldRestorations]

Possibly scavenge around eBay or something like that for parts. The entire sending unit is Yamaha P/N 42H-85752-01 (all the same from 84 to 99). This includes the thermistor can, bracket and wire. You might be able to search that part number and come up with a decent quality used unit. You can use a round o-ring in place of the Yamaha OEM one as long as the cross section and diameter are the proper size.

[@gabrieldaza7071]

Friend, what other thermistor can I use? since where I live I have only gotten 120 ohms and 4.5k

[@KensWorldRestorations]

Hi...the thermistor needs to be exact. The circuit is designed to use that value and only that value.

[@gabrieldaza7071]

@@KensWorldRestorations I have gotten 1k but it is linear, is it possible?

[@KensWorldRestorations]

@@gabrieldaza7071 So long as it is an NTC thermistor, you'll be ok.

[@Fireballspc]

Dear KensWorld I live in Brazil and I'm looking to buy a 1996 XV750 and I've been looking at the manual and I saw that it has an oil light on the dashboard, but I didn't see this switch on the engine to turn it on, Do you know how these sensors work? Would it be similar to this gasoline one with PTC sensor? In this case, when the fuel level drops and there is no heat dissipation than the lamp current that will heat the PTC and light the lamp? the current would be too low to heat the PTC and light the LED .... Correct? Thank you....Fire

[@KensWorldRestorations]

Hey Fire. The sensor for the oil is an oil level sensor in the crankcase. It is located at the bottom front of the engine on the right side right under the oil filter. There is a metal cover over it. The sensor works the same way as the low fuel sensor but it's a different one. The oil sensor only senses a low oil level, not pressure. When you start the bike and push the start switch, a relay under the seat turns the light on so you know that it works. When the oil level is low, the light should come on if the switch and light bulb are ok. The switch is the same for almost every Virago out there - 700 through 1100.

[@Fireballspc]

@@KensWorldRestorations ok my dear, But in this case, would it be the switch that turns on the oil lamp type NC (Normal closed)? ....actuated by a float with a red witch or suddenly by a micro switch? I have a BMW E46 325 car that the coolant sensor is inside a red switch NO (Normal open) if the level drops a float with a magnetic ring triggers the red switch and turns on a low level light on the dashboard. Thank you... this clarification helped me a lot.

[@KensWorldRestorations]

@@Fireballspc I'm not completely sure if the oil level switch in the Virago is NO or NC...I can test it tonight and get back to you. It is not mechanical at all - there are no moving parts. It is simply a couple of contacts that sens the level of the oil. Follow this link for a photo. tinyurl.com/yck8turb.

[@Fireballspc]

@@KensWorldRestorations Yeah, I saw the link and the oil sensor and I could see and imagine that it only has that wire that appears and the closure must be due to the grounding of the engine frame. So I imagine that when the level drops you must ground this wire through the sensor and turn on the lamp. If you can measure this and then let me know, thank you. But it doesn't have to be today, when you have some free time. An interesting thing that crossed my mind, is that in a future oil change, when draining the center stand, leave the key on and see the moment when the lamp lights up due to low oil level, then restart the rest drain and check how many liters it has when the light comes on. For safety I think it should be about half the volume (3.1 liters) ... that is 1.5 liters or almost half a gallon Thank you.

[@KensWorldRestorations]

@@Fireballspc If you do the test you mention above, remember that the system has been designed and calibrated to warn of a low oil level when the engine is running. Some of that oil will be circulating and some will be in the sump. At least the drain test will confirm that the circuit is working properly. I measured my sensor and it is NC with respect to chassis ground when there is no oil in the crankcase. Once oil covers the sensor, it opens the circuit. Hope this helps!!

[@matisok]

Excellent video. I am about to engage in the same repair - following your video. Do you think I need a test jig like yourself? My fuel light comes on at ignition (briefly) as I should I believe, but doesn't come on when the engine is coughing for fuel and I switch to reserve - I guess that it clearly a faulty fuel sensor then. Mine is a XV750 from 1993.

[@KensWorldRestorations]

Hi Mathias - if your bike is a 750 then it doesn't have a fuel pump. The circuit is different on the 700/750 compared to the 1000/1100. I'm not sure how the 750 circuit works to be honest but I do know that the750 has a manual petcock for reserve. What country was your bike manufactured for?

[@matisok]

Hi ya. Yes, true it has a manual petcock. I was assuming that the fuel sensor was the same - maybe I should just open her up and investigate. It's not really a big deal not having the fuel light working - I just flick to reserve once the bike starts coughing and I can see on the odometer that I about to reach the reserve. But it would just be nice if the light was working and then some of us are also looking for any excuse to spend time on taking the bike apart :) - Country: Denmark.

[@KensWorldRestorations]

Yes...of course. I think I misunderstood. The sensor should be the same - it should behave in the same fashion as the 1000/1100 so if your light bulb is good then it’s probably the sensor. They usually fail open. I don’t think you’ll need the little tester I made, but having a decent multimeter will be beneficial. If you unplug the tank, you should measure somewhere between 500 ohms and 1.5K ohms if the thermistor is alive and well. An open circuit shows a dead thermistor. And yes, it’s always nice to do exploratory surgery...you get to learn so much about the bike!! Keep me posted!!

[@matisok]

@@KensWorldRestorations hi ya. While waiting for the delivery of a 1kohm thermistor I was fiddling with the bike as usual. The fuel tank was nearly empty and to my surprise the fuel level detection was working! It just seem not turn on before the bike starts coughing - so maybe it's slightly misplaced in the tank. Because it turns out that when I tilt the bike the light comes on. I made a video of it here just for reference. kzbin.info/www/bejne/o6ikc2ucjK9sgsk Thanks for your help again- now I suppose I should open her up and see if I can figure out now to adjust the place of the sensor.

[@KensWorldRestorations]

@@matisok Great discovery! The thermistor should be in a small brass can and maybe the can has slid down the attachment point. Glad you got it all figured out.

[@kevinruddy448]

Because its got no petrol tap ⛽🏍️🙄?, wierd?