FJowners.com

My biggest guestion is how reserve switch work and how fuel supply is cutted off when engine is not running my bike is 3cv, i coud´nt find
real pics from Haynes Manual( there were pics something vacuum lines to tank and solenoid, i have not these things  only one line to pump on my bike) . Is the fuelpump only thing that cut off fuel supply or are the needles only thing. hope you understand friends.

Uh Oh....  (popcorn)

Uh oh is right, we had a long discussion on this issue.. (popcorn)

We all agree that when the fuel level in the tank reaches a certain point the reserve function is triggered and the bike begins sputtering...or stuttering..

On the '89-'93 fuel pump FJ's I think we all agree that the reserve function, when triggered, turns off the fuel pump, the bike sputters, until the switch is moved to reserve, at which point the fuel pump starts again.

What we don't agree on is on the gravity flow '86-'87 FJ's exactly what causes the bike to sputter or stutter.

Here's where we stand today:
Some say it is due to a interruption of fuel to the carbs...petcock shuts off...the bike sputters, then recovers when reserve is activated
Some say it is a ignition timing interruption. The ignition box interrupts timing and the bike stutters, until the reserve is activated.

The wires going to the tank petcock suggest something to do with fuel interruption.

However...when the bike starts studdering and reserve switch is activated (switch moved to reserve)....the studder stops immediately..like it's electric..bike comes back quicker than the time it should take for gravity to flow the fuel to refill the carb bowls....in other words, the bike responds like the timing interrupt is turned off...
Fuel flow interruption (sputter) would (should) take a longer recovery period than what happens.

So is it a ignition stutter? or is it a fuel sputter? We don't agree....

That's the best of my recollection on this subject.

So what do the '84/'85 models do?  Their petcocks don't have wires. 

Will they sputter first, or run fine until empty and shut off?

You should go verify this on your '84 Pat.  It's for the good of the community.....

Small steps first.
With your engine off, there is a check valve in the fuel pump to stop fuel flow. (these have been known to fail).  Next is the needle and seat valve. That's it.

The 1988-93 bikes have a plain petcock with a screen filter. There is a small white plastic shaft that you can manually turn the fuel off but it difficult to get to in a hurry and from memory a 9mm wrench will fit the tab. The picture you are referring to is for an older version of the fuel reserve system.  Also on the 88-93 bikes there is a fuel filter mounted on the bottom side of the tank.

(http://fjowners.com/gallery/6/1651_08_10_13_10_59_09.jpeg)

Roughly when the sensor in the tank sees low fuel level it will send a signal to the fuel pump relay to turn off.  When you hit the reserve switch all it is doing is reestablishing power to the fuel pump relay. (IMO)
(http://fjowners.com/gallery/5/1651_26_09_13_4_44_58.jpeg)

Here is a thread probably worth reading through.

http://www.fjowners.com/index.php?topic=9996.0 (http://www.fjowners.com/index.php?topic=9996.0)

George  ("HI Mike"  (popcorn))

Interesting ....... I am going to remove the system completely . I don't have the whole switch , black plastic framewith two contacts only...do I have to leave them off or on permanent? Thanks a lot

Quote from: FJ_Hooligan on July 17, 2014, 05:22:17 PM
So what do the '84/'85 models do?  Their petcocks don't have wires. 

Will they sputter first, or run fine until empty and shut off?

You should go verify this on your '84 Pat.  It's for the good of the community.....

uuuuh, yea, let me take the bike out on a desert back road this afternoon.....is it a sputter or stutter?

....sure won't have to worry about frostbite...

Quote from: glukasil on July 17, 2014, 05:44:22 PM
Interesting ....... I am going to remove the system completely . I don't have the whole switch , black plastic framewith two contacts only...do I have to leave them off or on permanent? Thanks a lot

Why take it out of the system?  Just get another switch or adapt an other switch from Radio Shack.  Used switches are probably not that expensive.

Reason: The reserve can be triggered at the most inopportune times....it's a stupid redundant system designed for stupid people.

You have a fuel gauge
You have a low fuel light
You have a odometer.

If you need a function that, in the middle of passing cars, causes your motorcycle to stutter..or sputter...whatever the fuck it does...then you should closely evaluate your ability to ride a motorcycle.

Just asking :)...  Like you I stop every 150 + - miles and refuel.  Never had a problem. Knock on wood...  I don't rely on the reserve system but it doesn't do any harm either.  If someone insists on running it down to the reserve point then potentially the same person will run there tank down to empty also.

When I say "insists on running it down to the reserve point" I know there are times that someone would have no choice.  Lack of fuel stations, 3 AM and no money etc.. Stuff happens in the real world.   :drinks:   I think back on fintips adventures in Oregon and N Calif.. pushing his FJ to the next exit....
George

Lets not forget about Fred and his plan, to attempt to go three hundred miles on a single tank of fuel. I am surprised he has not started a topic on how far have you gone on a single tank of fuel.

Kurt

I stand by my earlier statements on the other topic, the fuel reserve system changes the duty cycle of the coils and causes the ignition to studder...

I have now been able to back this up on a couple of projects I am currently working on.

#1) The RPM EFI on my 86 does not use the stock CDI anymore and the bike not longer has an ignition studder...it just runs out of gas and comes to a stop.

The light on the dash still illuminates, but since the Yamaha CDI is not longer present no ignition studder.
Now, I have to get my fuel gauge needle back to the other side of the dang pin cause this FJ is heavy to push...

#2) I am working on a 90 that has a Dyna ignition system installed which still uses the tach signal to keep the fuel pump running. After 5 or so seconds without the CDI seeing a tach signal, the fuel pump shuts off. Well, guess what it just runs out of gas too when the tank is empty. Again the light in the dash works, but there is no indication from the engine via ignition studder because Dyna does not have that function incorporated into their system. The fuel gauge works on this one and I ran it out of gas on purpose to see if the engine would be affected via the Dyna ignition.

So, that is where I stand on this topic...

...the same place I stood on this topic...Reserve Switch (http://www.fjowners.com/index.php?topic=9996.msg99506#msg99506)

Randy - RPM

Whoa Cowboy....tell us a bit more about your '86...didn't you bypass the vacuum petcock function (so it's open all the time) along with disconnecting the petcock wires?

....of course you have no reserve function....

Quote from: Pat Conlon on July 17, 2014, 08:51:07 PM
Whoa Cowboy....tell us a bit more about your '86...didn't you bypass the vacuum petcock function (so it's open all the time) along with disconnecting the petcock wires?

....of course you have no reserve function....

Nope, the petcock is still vacuum operated  with the wires still hooked up, thats how the light on the dash still works...

Randy - RPM

Quote from: racerrad8 on July 17, 2014, 08:58:28 PM

Quote from: Pat Conlon on July 17, 2014, 08:51:07 PM
Whoa Cowboy....tell us a bit more about your '86...didn't you bypass the vacuum petcock function (so it's open all the time) along with disconnecting the petcock wires?

...of course you have no reserve function....

Nope, the petcock is still vacuum operated  with the wires still hooked up, thats how the light on the dash still works...

Ok, that's that...case closed....however....The fuel light is activated by the sensor on the float assembly....not by the wires on the petcock.
At least that's how my '84 and '92 works.....I know this is true 'cause they have no stinkin wires on their stinkin petcocks...

Guess what?
Did you know that all our FJ's from 1984 to 1993 use the same gas tank float assembly? I didn't know that:

Description
Purchase this Yamaha 36Y-85752-03-00 SNDR UT ASY,F/MTR --- SNDR UT ASSEMBLY, F-MTRFUEL MET, SNDR UT ASSY, F-MTRFUEL METER
This Yamaha 36Y-85752-03-00 SNDR UT ASY,F/MTR is used on these models and components:

1984 FJ1100L ELECTRICAL 1
1984 FJ1100LC ELECTRICAL 1
1985 FJ1100N ELECTRICAL 1
1985 FJ1100NC (CA ED.) ELECTRICAL 1
1986 FJ1200S ELECTRICAL 1
1986 FJ1200SC (CA ED.) ELECTRICAL 1
1987 FJ1200T ELECTRICAL 1
1987 FJ1200TC (CA ED.) ELECTRICAL 1
1989 FJ1200W ELECTRICAL 1
1989 FJ1200WC (CA ED.) ELECTRICAL 1
1990 FJ1200A ELECTRICAL 1
1990 FJ1200AC (CA ED.) ELECTRICAL 1
1991 FJ1200B ELECTRICAL 1
1991 FJ1200BC ELECTRICAL 1
1992 ABS - FJ1200AD ELECTRICAL 1
1992 ABS - FJ1200ADC ELECTRICAL 1
1992 FJ1200D ELECTRICAL 1
1992 FJ1200DC (CA ED.) ELECTRICAL 1
1993 FJ1200AE ELECTRICAL 1
1993 FJ1200AEC (CA ED.) ELECTRICAL 1

So, my question remains....what is the purpose of the wires on the '86/87 fuel petcock if not to (at least partially) interrupt the fuel flow?
We know it has nothing to do with the low fuel light.

Hmmmm.... all very interesting.
I have full Dyna 2000 system on my '91.......OEM cdi disconnected completely (ie......no connectors plugged into it at all).

If I leave my fuel reserve switch in the on position, the pump does not run and she runs out of fuel -  I leave the fuel switch in the reserve position all the time.
When I turn the ignition switch on the fuel pump runs for 5 or so seconds and then stops...... I can switch of and back on as many times as I like and the same thing happens..... and it does NOT flood the carbs.
The only other consideration in this is that I do not have an OEM fuel pump either.

I doubt this helps the discussion, and the whole behaviour seems odd to me, but it works and it has never let me down, so that's the way its staying.

Cheers
Harvy

 (popcorn)

Without doubt my favourite discussion over the last 5 years. Thanks for the chance to read it again.

(popcorn)

Noel

Thank's Harvey, interesting observation..

I was surprised at Randy's answer...that he still uses the vacuum shut off feature of the '86 petcock with his fuel injection system.
My thinking was that when the key is turned on, the fuel pump runs and pressurizes the fuel rail and injectors.
I assumed this could not happen with a closed petcock.