advice needed, R1100s stopped running

Merecat · Post by **Merecat** » Thu Jul 03, 2014 2:48 pm

Had a similar thing on a CBR600. The pump refused to run on the bike despite 4 carbs pulling the fuel out of it.
Give it 12V off the bike and it would chug away all day.

The conclusion:
Fuel pumps:..........Like women, difficult to understand

Sits back and watches the thread degenerate

Duggers · Post by **Duggers** » Fri Jul 04, 2014 11:23 am

Some things I've noticed

It ticking over more evenly
Generally running smoother off a small amount of throttle
It had developed a tendency to stall when trying to pull away from a standstill, I thought this was me being ham fisted but it's stopped doing it
The tyres have more grip
The world is a better place

Maybe, just maybe, some of this is imaginary but it's amazing how much better things feel when you are back on a bike.

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Corvus · Post by **Corvus** » Sat Jul 05, 2014 9:15 am

Merecat wrote:Had a similar thing on a CBR600. The pump refused to run on the bike despite 4 carbs pulling the fuel out of it.
Give it 12V off the bike and it would chug away all day.

The conclusion:
Fuel pumps:..........Like women, difficult to understand

Sits back and watches the thread degenerate

Can't fault your conclusion!

It's an interesting one. The pump must be sized to provide positive head against the fully open needle valve orifice, to cater for wot flat out out running, presumably? But then not so much as to overcome the buoyancy of the float, via leverage, onto the needle valve, taking into account the diameter of the needle valve orifice, for less than wot running? But still always a positive head?

Wonder what the pressure actually is?