Fuel reserve systems?

[racerrad8]

We know there is a safety circuit that shuts off the power to the fuel pump after 3-5 seconds if the engine is stopped.
After servicing your carbs and you reinstall them with the fuel bowls empty, when you turn your key on, notice that the fuel pump runs for only a couple of seconds then shuts off? You have to turn the key off, then on, a couple of times for the pump to fill the bowls.....that's the safety circuit.

That is for when you crash, then engine hopefully dies and the fuel pump shuts off.

I doubt that has anything to do with the reserve system.

Randy - RPM

[Pat Conlon]

Randy, that's correct, my point was that the fuel pump is controlled thru the ignition box. The safety shut off is an example.

Again, when my '92 ran out of gas (not on reserve) the bike stopped...Yes it started as a studder until it got worse, and the engine died.

Flipping the switch to the reserve position restarted the fuel pump. I could hear it. Only then did the bike start.

This is easy to check, although you have to be stopped with your helmet off to hear it.

[Flynt]

Could the reserve system be both, fuel and spark?  

This was the conclusion we reached last time around...  Randy produced a drawing that showed impacts on both the pump and the ignition more or less.

Frank

[Flynt]

There it is...

http://www.fjowners.com/index.php?topic=9996.msg99645#msg99645

Looks like it was my conclusion alone.  It looks like it could easily do both spark cut and fuel pump interrupt.  Evidence seems to support that is what we're seeing.  The only question to answer now is why would they design it that way...?

Frank

[Bones]

Last year after arriving at the Mapleton Muster, my bike started running a bit rough and was down a bit on power, pulled up at the servo to top up fuel and noticed it was idling on three cylinders, gave it a few revs and it revved ok though still only on three cylinders. Checking it later at the cafe with the engine running  I was thinking it was either a bad plug or lead, before suddenly getting worse and stalling. Straight away I heard the fuel pump clicking like mad and no matter how many times the key was turned on or off it wouldn't build pressure, so did a pump bypass and the bike ran like a train for the rest of the day.

What I'm getting at though is that even though it turned out to be a fuel starvation problem, it gave the distinct symptom initially of being an electrical problem, so owners of pre fuel pump models with a working reserve can try this out, next time fuel is getting low and it starts to stumble, keep going without flicking the reserve switch on and see what happens, If it goes for another 10/15 miles down the road but keeps stumbling, it's safe Id reckon to say the reserve affects ignition, if it stops a mile or so down the road it affects fuel.