Fuel Reserve

[Cass]

Evening Gents new to this forum. I am rebuilding a 1993 FJ1200 which had been sat for 7 years after the previous owner died. Stripped it all down and have been reassembling it and have now got to the fuel system. I have a fuel reserve switch next to the choke which plugs in to the harness. I have a stop cock on the bottom of the tank which has a single pipe which goes to the fuel pump with an inline plastic fuel filter. The fuel pump is connected to the wiring harness. I have a fuel line from the pump to the carburettors.
Can someone tell me how the fuel reserve switch works? What does it activate? Am I missing something and if so what and where should it be?
According to the Haynes manual I should have a solenoid type switch either between the tank stop cock and the fuel pump or instead of the stop cock but I have nothing and there was nothing on the bike when I stripped it down.
Any help would be appreciated. Diagrams of the set up or photos would be great.
Rob.C.

[Mike Ramos]

Evening Gents new to this forum. I am rebuilding a 1993 FJ1200 which had been sat for 7 years after the previous owner died. Stripped it all down and have been reassembling it and have now got to the fuel system. I have a fuel reserve switch next to the choke which plugs in to the harness. I have a stop cock on the bottom of the tank which has a single pipe which goes to the fuel pump with an inline plastic fuel filter. The fuel pump is connected to the wiring harness. I have a fuel line from the pump to the carburettors.
Can someone tell me how the fuel reserve switch works? What does it activate? Am I missing something and if so what and where should it be?
According to the Haynes manual I should have a solenoid type switch either between the tank stop cock and the fuel pump or instead of the stop cock but I have nothing and there was nothing on the bike when I stripped it down.
Any help would be appreciated. Diagrams of the set up or photos would be great.
Rob.C.

The reserve switch....?

Uh Oh... the next question you can expect is what is the best oil...?! 

[ZOA NOM]

 


edit: that isn't a very useful answer for OP, but I gave up on my reserve switch long ago, and rely only on my trip meter. Reset every fillup and get nervous above 200 miles.

[FJ_Hooligan]

The petcock on a '93 is only on or off.  The line runs from the petcock, to the filter under the tank then to the fuel pump as you described.

From what I experienced on my '93, when the fuel level gets low (amount left will vary from bike to bike) the fuel pimp circuit will shut off causing you to experience what it feels like to run out of fuel.  Flipping the reserve switch restores power to the pump and will allow you to run the tank to empty without further intervention.  Once you activate the reserve function, fill up as soon as possible.

[Cass]

The reserve switch....?

Uh Oh... the next question you can expect is what is the best oil...?!  

Obviously you did not read the questions I was asking or you might have been more helpful. I asked how it worked as it is not obvious. It is quite clear from your reply that you know as little as I do about the reserve operation. Maybe oil is your speciality and you should stick to it! Thanks for your input.

[Cass]

The petcock on a '93 is only on or off.  The line runs from the petcock, to the filter under the tank then to the fuel pump as you described.

From what I experienced on my '93, when the fuel level gets low (amount left will vary from bike to bike) the fuel pimp circuit will shut off causing you to experience what it feels like to run out of fuel.  Flipping the reserve switch restores power to the pump and will allow you to run the tank to empty without further intervention.  Once you activate the reserve function, fill up as soon as possible.

Thank you FJ Hooligan that explains a lot. It was not very clear looking at what I had on the bike how it worked and I did not have a operators manual come with the bike. Thanks for your prompt and informative reply.

[great white]

The reserve switch....?

Uh Oh... the next question you can expect is what is the best oil...?!  

Obviously you did not read the questions I was asking or you might have been more helpful. I asked how it worked as it is not obvious. It is quite clear from your reply that you know as little as I do about the reserve operation. Maybe oil is your speciality and you should stick to it! Thanks for your input.

Nah, it's kind of an inside thing on this forum about the reserve switch. There's been years of debate on how it works, what it does and such. Literally years and probably thousands of posts on it. Kind of a hot topic with as many opinions as....well, which oil is best to use.

You just had the misfortune to stumble into it, not knowing the history. Kind of like running around a corner and going face first into a hornets nest you didn't know was hanging there.......

But, it is an on/off thing. The bike will start to "stutter/miss/etc" once the fuel level reaches a certain point.

The debate is on what the switch actually does, since it's not a traditional style petcock where there is a stand tube inside the tank. Some say it cuts ignition, some say it turns off the fuel pump, some think it's the pull of the moon on the fuel level in the bowls.........(I kid).

I personally, do as an above poster, as I have with all my bikes through the years: set the trip, start looking for fuel up when I know I'm getting close. If it starts to sputter, walking is imminent (in my mind at least). Toss the RES switch and hope it has enough for you to find the next gas stop.

I also don't particularly trust the "electronic res" switch on the FJ. Sure, it works, but I don't have the confidence in it reading the fuel level as I do with a stand pipe petcock where I absolutely know beyond a shadow of a doubt there's so many gallons left when it starts to sputter.....

[Pat Conlon]

I thought that was put to bed several years ago....the reserve switch re-activates the fuel pump...period.

You can hear it clearly.

[racerrad8]

The reserve switch....?

Uh Oh... the next question you can expect is what is the best oil...?!  

Obviously you did not read the questions...

Oh, he read it...

It has been cover at length with, arguably, no clear understanding.



Reserve Switch

Randy - RPM

[racerrad8]

I thought that was put to bed several years ago....the reserve switch re-activates the fuel pump...period.

Pat, after looking at the circuit many more times I am still not convinced or been shown the that the fuel pump is shut of...period.

Unless there is a turbo fill function like Harvy said way back then...

Look at #3 of the operation in the schematic below...
       "Determining timing for switch on ignition coil (duty cycle)"



And then, I do not see the "reserve switch" listed, shown or mentioned in the "fuel pump circuit" below.



I still stick with my theory of the CDI receiving the low fuel reading from the sender. It then changes the duty cycle of the coil drivers. The bike then misfires, but not so much it would affect the performance. Once the "reserve" switch is toggled, the proper duty cycle is then re-activated and the bike runs at full song.

If not, please, please, please explain to me how the bike instantly comes back to proper running/full power without having a delay of refilling the fuel bowls since the fuel pump has been turned off and the fuel bowls are running dry.

Randy - RPM

[Mike Ramos]

The reserve switch....?

Uh Oh... the next question you can expect is what is the best oil...?!  

Obviously you did not read the questions I was asking or you might have been more helpful. I asked how it worked as it is not obvious. It is quite clear from your reply that you know as little as I do about the reserve operation. Maybe oil is your speciality and you should stick to it! Thanks for your input.

Hold on a minute... obviously you did not read the series of posts from several years ago or you might have been a little less....  Oh forget it!

Hey Cass, lighten up, sometimes just having a bit of fun is the way to go - so let's not get too serious; laughter is the best medicine...!

[The serious thing is to always] Ride Safe,

Midget

[Pat Conlon]

It's quite easy to find out for your self:

Run the bike until it stumbles and the engine dies. Clutch in, pull over to the side of the road. Take your helmet off and ear plugs out so you can hear. Now turn the key off, and then on. Do you hear the fuel pump? The usual 3-5 second chatter ((before it times out) when you turn the key on? No, you don't.

Wait! You say you don't hear the fuel pump because the bowls are full....

Here's the kicker:
Now turn the reserve switch to reserve and turn the key on.
You will now hear the fuel pump chattering away.

If it was ignition interrupt I would expect to hear a pop or backfire from igniting all the accumulated unburned fuel. The same sound you get from today's quick shifters which use ignition interrupt.
You will say, but it's a soft stumble, Ok, that would prevent that, but, tell me.
If it were set as an ignition interrupt why does it get progressively worse?
To a point where the engine dies. Why can't you just limp along with the stumble? Why kill the engine?

Like I said: It's easy to find out yourself (just don't do it on the freeway)

[racerrad8]

OK, next time I run out of gas I'll check it out. But not something I think will happen anytime soon.

As far as your backfire theory.

I did not say shut the ignition off which will then flood the cylinder with unburned fuel. Then once spark is introduced a backfire occurs due to the unburned fuel in the exhaust pipes.

I am saying reduced duty cycle causing misfire.

Now, the explanation on how the engine comes back to life instantly with the flip of the reserve switch. I previously posted a video of your bike stumbling as the carbs refill.

I did this with your bike to make sure there was no question about the electrical reserve system. Your bike does not have it.

So, what is your take on the instantaneous change with the flip of the switch, what happens?

Randy - RPM

[Pat Conlon]

Sorry Randy, I was modifying my post when you responded...

My '84 doesn't have that silly reserve system. It's a big boys bike. No nanny here.

My theory is that for the bike to start to stumble, the fuel level in the bowls just has to be a *tiny* bit low at the pilots.
The rider flips the reserve switch before the fuel level gets too low, and the pump cycles back on and "quickly"
brings the fuel level back up to the level of the pilot jets.

We are not talking about the time it takes to fill up an empty bowl, nothing like that.
Just the time it takes add a millimeter (or two) of fuel to the bowls.

[racerrad8]

A few questions based on your theory.

1) So, there is a "quick fill" function of the fuel pump.

How does that work?
Regulated voltage to the pump?

2) Are you implying the pilot jet circuit is still in play at 60 mph?

If that is not the case, how does the engine start to sputter when the pilot circuit is not in use?

3) finally, since the only function is the fuel pump being shut down how do you explain the function of the 86-87 reserve system.

There is no "quick fill" option there. So how does the gravity feed system quickly refill the carbs?

Randy - RPM