Topic approved.

I dont know for sure wether it is correct, but they say that if the fuel supply is less to the FI pump it gets heated up and burns and that leads to costly issue of replacing the pump, thats what I heard.. But I have rode a R15 till the empty tank but did not face any issue I just filled it up and it is running normally!

I have seen my fren'z RTR Fi many times, and it always runs in reserve. So far there is no problem with his bike or the Fi system. He is getting an average of 40+ and the ride is 18k on odo.

This is the first time I am hearing this type of a problem. I will ask my friend to talk about this at the ASS.

Would be nice if you could throw some light on how and where you heard about this?

Google & xBhp gives...

One clarification: In most FI systems, pumps no longer 'pull' fuel from a tank but in fact 'push' fuel from inside the tank itself.

Two reasons for maintaining a certain minimum fuel level .

1. The bikes are fueled by submersible pumps that are run by small, high-torque motors. The fuel they are immersed in acts as a heat sink and keeps the motor and pump body cool.

2. Remaining immersed under fuel is important for the pump to be able to generate sufficient fuel pressure in the fuel line to keep the engine running.

But why don't the same rules apply to cars?

A bike has another degree of freedom in movement i.e. around its rolling
axis. Even if the fuel level is sufficient with the bike upright, it might fall below the minimum when the bike tilts. Cars don't tilt all that way.

Also bikes probably have pumps that are not self-priming. So if the inlet to the pump gets exposed to air while the pump is 'on', it might result in a vapor lock/air lock inside the pump and even filling up fuel will not help in getting the pump back to building up fuel pressure. And since bikes can 'jump' about a lot while in motion, a low fuel level could momentarily make the fuel level go below the inlet, allow air to enter and so stop further fuel flow to the engine.

can somebody explain more technically the issue of motorcycle fuel pumps

Sir just a small doubt. But doesnt such immersion of the fuel pump in the fuel be dangerous?? As the fuel pump runs on electricity & if even a small spark occurs then it can result in the ignition of the fuel around it??
Please throw some light on it.

Yes Madhav, motors and electricals can spark and do so in the case of these pumps too. But the fact that you need the trio of fuel, heat and oxygen to start a fire comes to the rescue here. With the pump fully immersed in the fuel, there's no air to start combustion. So the fuel doesn't catch fire. Thats also probably one of the reasons why it is important to keep a minimum fuel level in the tank. Though as a redundant safety measure, the pump's electric supply gets cut off if any of the conditions like heating of the pump, drop in outlet pressure indicating low level at inlet, sudden impact (inertia switches) and roll-over of the bike. I cannot vouch for the fact that all this is a part of the FI bikes being manufactured here but that's pretty much the norm for FI engined vehicles.

Not sure about this what you said. I am not a tech guy but as far as I know vapor lock/air lock is taken care by an external pump. So air shoudn't enter your engine?? not only in Fi engines but it was the same even in my old ZMA..Isn't that right

Thanks for the answers OF Sir; it took a while & I'd to read it multiple times to understand & hence the delay in response.

This is news to me as I was always under the impression that fuel is always being pushed.

And from your replies, I can think of one more reason - avoid fire being immersed.

Couldn't get this point OF Sir; can you help me understand pls?

Again, I couldn't think in this direction. I was always thinking as the fuel is being pushed. Appreciate to throw some pointers on air inlet tube.

OF Sir - from your post what I understood is that, the FI pump in motorcycle is something like a submersible water pump that is sunk in water & pushes the water up to the over head tank. If the water dries up the motor burns. This is exactly what I can relate. Pls guide if my understanding is incorrect.

On the other hand, I couldn't help thinking, why the manufacturers could not adopt a fuel pull motor technology like in the car so that the reserve also could be used?

Few sources from net on FI
1. Harley-Davidson Motorcycle Fuel Injection Explained
2. How Electronic Fuel Injection (EFI) Works - Motorcycle Cruiser Magazine

hmmmm
i am riding my zmr in reserve from months ....but touch-wood i have not faced any problem till now

by the way
if i fill more petrol i would end up riding more & again bring it to reserve on the same day

Reviving the thread to post addition info that I came across - Jbabs's Fuel Injection Page

in the 1st link i.e. EFI in harleys, there is another link that leads to a table EFI terminology
in that, they have mentioned a senor by the acronym BAS(bank angle sensor). As per my understanding, this thing safeguards the FI against entry of air by switching off the engine whenever it exceeds a certain bank angle.
My question is can't things like his be developed and incorporated in to desi FI bikes?

edit: but then again, if the bike goes over a bump(highly probable on Indian roads) then the BAS won't be able to do anything at all
btw, thanks for the links

edit 2:another thought- why don't the FI manufacturers provide an indicator in the bike's console for the 3L level? Even after that if the owners show up with blown up injectors wanting to claim warranty, then the company will atleast have a strong point for defending.