Fuel Reserve

[Pat Conlon]

With Dave's experience on his '86, we can rule out ignition interrupt and a function of the reserve.

Pat, are you sure Dave's bike is not stuck on reserve based on his new theory...?

Yes, I believe Dave's petcock is stuck on reserve....and my statement was not based on theory, it's based on evidence.
Dave's evidence shows that he completely drained his tank with no hint of ignition interrupt.

[racerrad8]

With Dave's experience on his '86, we can rule out ignition interrupt and a function of the reserve.

Pat, are you sure Dave's bike is not stuck on reserve based on his new theory...?

Yes, I believe Dave's petcock is stuck on reserve....and my statement was not based on theory, it's based on evidence experience
Dave's evidence experience shows that he completely drained his tank with no hint of ignition interrupt.

FTFY...

You need even said so in your posted theory.

Randy - RPM

[racerrad8]

Randy, my low light flickers for a few miles prior to illuminating solidly.  Does your bike stumble when the light begins to flicker or does it start to starve only when the light is on solidly?

My 86 starts stumbling as the light starts glowing. I can jamb on th front brake, shut the light off and the light goes out and the stumble stops immediately.

My wife's bike bulb goes to a bright illumination before it starts to stumble. It glows lightly, getting brighter as the level drops. Since I can't watch it all the time, I'm not sure how much brighter it gets. I have usually switched over already because the bike runs so poorly.

Again, there is no delay on the return of proper engine operation at the flip of the switch.

Randy - RPM

[ct7088]

My 85 has an 86 tank. The 86 tank came with the electrically operated reserve petcock which I'm using because it is smaller and easier to put the gas line on. The connector for the petcock isn't connected and it will drain the tank. When the reserve light comes on solid it is time for more gas. Reserve function equals an open circuit.

Chris

[Capn Ron]

I like to know how things work, but this is one that I'm happy to give up on.

With newer bikes having a fuel pump and the older ones not, three different petcock designs over the years, old magazine articles referring to a coil shutdown, some bikes having a low fuel light and some without the light, the changing approach to the reserve function by Yamaha over the generations of FJs, reserve switches that may or may not work after 25+ years on a specific owner's bike, possible fault with an electrically operated petcock and any other intermittent failures after 30+ years, the permutations here are mind boggling.  It's no wonder there are no solid conclusions.

Even to begin, one would have to first separate the generations (or specific year being discussed), then each system (switch, fuel light, petcock, etc...) would have to be known to be functioning as it should be (even that is in question).  Only then could a test be done to see if it's a coil, or a petcock or a fuel pump cutoff.  Then you have to start over for another generation/year.

I applaud those who are hanging in there to find the answers! 

[great white]

Well, my 89 isn't going to shed any light on the issue. I finally got the level low enough to bring the fuel light on when leaning on the side stand and.....nothing.

With the res switch on or off it happily rattled along. No change at all. Seems I'm on res all the time I guess. No big, I use my trip odo anyways, its just something I've always done. I might chase it down this winter to see if it's a switch issue or something in the wiring....

[ribbert]

I like to know how things work, but this is one that I'm happy to give up on.

With newer bikes having a fuel pump and the older ones not, three different petcock designs over the years, old magazine articles referring to a coil shutdown, some bikes having a low fuel light and some without the light, the changing approach to the reserve function by Yamaha over the generations of FJs, reserve switches that may or may not work after 25+ years on a specific owner's bike, possible fault with an electrically operated petcock and any other intermittent failures after 30+ years, the permutations here are mind boggling.  It's no wonder there are no solid conclusions.

Even to begin, one would have to first separate the generations (or specific year being discussed), then each system (switch, fuel light, petcock, etc...) would have to be known to be functioning as it should be (even that is in question).  Only then could a test be done to see if it's a coil, or a petcock or a fuel pump cutoff.  Then you have to start over for another generation/year.

I applaud those who are hanging in there to find the answers! 

Ron, the reserve switch function on the fuel pump models was settled to most folks satisfaction a couple of years ago. I'm sure the earlier models are no more complicated to figure out.

The scenario you outline of nutting out all the different generations and systems really just describes an ordinary day for a mechanic or auto electrician, it's their job and to them it's not difficult or confusing.

Noel

[Capn Ron]

Ron, the reserve switch function on the fuel pump models was settled to most folks satisfaction a couple of years ago. I'm sure the earlier models are no more complicated to figure out.

The scenario you outline of nutting out all the different generations and systems really just describes an ordinary day for a mechanic or auto electrician, it's their job and to them it's not difficult or confusing.

Noel

Well, get right on that then!  

[Super]

My KLR will stumble and die when it runs out of fuel, and by the time it takes me to return my left hand to the handlebar after twisting the valve to "reserve" the carb has refilled enough to keep the bike running.  I know, it happened to me last week whilst among highway traffic.  My old Seca 900 would fire back up almost immediately too so I  can attest float bowls fill quickly enough to give the impression the ignition was cut off.

Something on my 86 is not prompting the fuel valve to close once the fuel level drops to a low level.  Or that "something" is prompting the valve to close and the valve itself is stuck open.  I'll pull the tank and check the valve but it would be helpful if someone could confirm what triggers the valve to open and close.

Dave