reserve switch

[ribbert]

Negative Ron, It is just as George explains it above ^^^ it is a fuel pump interrupt.

I wonder where this 'ignition interrupt' idea keeps coming from?

We have been hearing it often....

Because it interrupts the ignition circuit on both of my 86's as they do not have fuel pumps...

Of course, that explains it.....

Not entirely, it still seems to be a widely held belief with the fuel pump models.

[RichBaker]

Ours uses an electronic "cutout" reserve...That means two cylinders will cut out giving you the impression you're running low on fuel and prompting you to flick the switch to "Reserve."  The owner's manual states the total capacity of the fuel tank as 5.8 US gallons
Cap'n Ron. . .

It does NOT "cut out 2 cylinders"!!!   It shuts OFF the fuel pump, causing the carbs to ACTUALLY RUN OUT OF GAS..... Please stop perpetuating this MYTH!    

When the low fuel light comes on solid, it signals the fuel pump relay to turn OFF, switching the rocker switch to reserve turns the pump back on.

[rktmanfj]

It has been said categorically here (by someone else thank goodness) that this is a myth. I agree.

If the coils were cutting out there would be an immediate return to normal operation once the switch is flicked. There is not.

I believe it cuts the fuel pump out.

The behaviour of the motor, both when it indicates the need to go to reserve and when the switch is operated is entirely consistant with this. That is, it takes a few seconds to kick back in after it has been flicked. That lag is the time it takes for the bowls to refill.

A motor deprived of fuel or spark has entirely different characteristics and the function of the reserve switch is consistant with fuel starvation, not spark interruption.'

For those that need it proved, it would be a simple test.

Noel

I agree with you , Noel, at least for the fuel pump models.   (I know...     )

The 'myth' was printed in one of the major magazine road tests of the day... I remember reading it.  I can't find it right right now, but this site poster seems to have 'cut and pasted' the text pretty much as I remember reading it, back in the day:

http://fjrireland.smfforfree2.com/index.php?topic=3.0

Electrical system
The FJ1200 features a standard 12 volt electrical system. The alternator and starter motor are mounted behind the cylinders. Yamaha's self cancelling indicator unit is used and a variable resistance gauging system is used to monitor engine oil contents with associated warning lights. A large fuel gauge is provided as is a low level warning light. Nippondenso Transistor Controlled Ignition (TCI) is used in conjunction with two coils. The FJ1200 fuel reserve system is unusual in that when the fuel level reaches approximately 5 litres remaining ignition is cut to two cylinders giving the impression that the vehicle is running out of fuel, a reserve switch mounted in the fairing restores the cut cylinders allowing the rider to continue normally.[7]

Unfortunately, his source isn't listed.     

[FJmonkey]

Of course, that explains it.....

[RichBaker]

Negative Ron, It is just as George explains it above ^^^ it is a fuel pump interrupt.

I wonder where this 'ignition interrupt' idea keeps coming from?

We have been hearing it often....

Because it interrupts the ignition circuit on both of my 86's as they do not have fuel pumps...

Of course, that explains it.....

Not entirely, it still seems to be a widely held belief with the fuel pump models.

I'm pretty sure the petcock, on the gravity-feed models, has a solenoid that closes the output off when the low fuel light comes on, simulating an out-of-fuel condition, same as the fuel pump bikes. That is why disconnecting the electrical connector to the petcock disables the reserve function....

[Capn Ron]

So, it was a mis-firing on the early bikes and a fuel-pump shut off on the later bikes?  That would explain my confusion at least.  And the point of ignition cut-off and fuel cut-off having very different performance effects on the engine is a good one.

I sit corrected...at least on the fuel pump models.    

Cap'n Ron. . .

[FJmonkey]

I'm pretty sure the petcock, on the gravity-feed models, has a solenoid that closes the output off when the low fuel light comes on, simulating an out-of-fuel condition, same as the fuel pump bikes. That is why disconnecting the electrical connector to the petcock disables the reserve function....

Going into the garage to check my old 86 petcock...

[RichBaker]

Cap'n,
See my last post, above yours....  I need to go thru the wiring diagrams for the 84-85, and 86-87 bikes, but I'm pretty sure NONE of them cut out 2 cylinders. I'm pretty sure they all cut fuel....

[FJmonkey]

Crap, I gave that part to Keand3 some time ago.... Sorry...

[Capn Ron]

I agree with you , Noel, at least for the fuel pump models.   (I know...     )

The 'myth' was printed in one of the major magazine road tests of the day... I remember reading it.  I can't find it right right now, but this site poster seems to have 'cut and pasted' the text pretty much as I remember reading it, back in the day:

http://fjrireland.smfforfree2.com/index.php?topic=3.0

Electrical system
The FJ1200 fuel reserve system is unusual in that when the fuel level reaches approximately 5 litres remaining ignition is cut to two cylinders giving the impression that the vehicle is running out of fuel, a reserve switch mounted in the fairing restores the cut cylinders allowing the rider to continue normally.[7]

Thanks for posting that...I read that same article back in the day.  It never occurred to me that they would change the way the reserve indication happens.  Before this campfire goes out, we'll have it settled, I'm sure.  

Cap'n Ron. . .

[RichBaker]

IIRC, Frank Moore found that disconnecting the petcock connector disabled the reserve function on the ambulances....

[movenon]

Negative Ron, It is just as George explains it above ^^^ it is a fuel pump interrupt.

I wonder where this 'ignition interrupt' idea keeps coming from?

We have been hearing it often....

Because it interrupts the ignition circuit on both of my 86's as they do not have fuel pumps...


Thing that make you go hmmmm

Randy - RPM

Going to have to think about the 84-87 FJ's  (stare into the digital camp fire) .

Different TCI/CDI/Ignitor box in the 84 - 87's. The 88-93's have a different ignitor box and wiring.   In the newer ignitors there is a wire e from the fuel tank reserve sensor to the ignitor box and a wire going from the ignitor to the coil of the fuel pump relay, it is the grounding side of the coil. When that "grounding" leg is interrupted by the fuel tank reserve sensor the fuel pump relay coil circuit turns off   (going to die, "may, day going down").  

Also going to the ignitor is one leg of the reserve switch to the ignitor box reestablish a ground condition inside the ignitor box for the fuel pump relay to relatch (great, now find a gas station). ??

Ron, the fuel sender has 3 wires. One ground, one fuel level and the other is from the "fuel low" sensor. Without tearing the little sensor apart I can't tell you how it operates. From the diagram it roughly looks like a balancing circuit between 2 resistors, when one side (the sensor) get enough out of balance it sends a signal to the ignitor. That's the best I can explain it.

Now can someone explain a 84-86 fuel reserve system as I don't one.  

George

OK the above post's gives me a good idea on how the early bikes work. The bottom line seems to be that all the FJ's by hook or crook cut the fuel off. Not the igntion system which makes more engineering since.

[Pat Conlon]

George, the 84/85's don't have the wonky reserve...just a low fuel level light (plus fuel gauge and odometer) that's why it is popular on the gravity flow 86/87's to retrofit the less expensive 84/85 petcock...to get away from the reserve switch.

I would like to confirm the nature of the interruption on the 86/87s.... fuel or ignition?

I'm almost certain the interruption on my '92 is at the fuel pump for just the reason Noel pointed out.

It takes a moment for my '92 to recover when switching to reserve....time for the fuel bowls to refill.
If it were ignition.....it would be immediate.

[RichBaker]

I'm at work, don't have a copy of my GYSM, but the complete description of how this works IS in there.... I don't want to download the copies available in the files section, too much hassle with the LAN here....

[movenon]

George, the 84/85's don't have the wonky reserve...just a low fuel level light (plus fuel gauge and odometer) that's why it is popular on the gravity flow 86/87's to retrofit the less expensive 84/85 petcock...to get away from the reserve switch.

I would like to confirm the nature of the interruption on the 86/87s.... fuel or ignition?

I'm almost certain the interruption on my '92 is at the fuel pump for just the reason Noel pointed out.

It takes a moment for my '92 to recover when switching to reserve....time for the fuel bowls to refill.
If it were ignition.....it would be immediate.

I am convinced from the wiring diagrams that all the newer bikes work by cutting the ground leg of the fuel pump relay breaking that circuit. They fuel starve.

I have a poor copy of an 86 - 87 wiring diagram and can see the reserve switch and the solenoid to control the fuel. The diagram I have is real small and hard to read.

George