Dies @ 120mph..?

[Goat_Herder]

or maybe it's your M750 telling you that it doesn't want to go that fast on public roads.  It wants to live long enough to see grand kids someday. 

[ducpainter]

So pulling that little black nipple worked for about 3 days but when my tank started getting low it went back to it's old ways. Thinking of going to a electric fuel pump, any ideas?

It sounds like your vacuum pump is weak/not working.

I think an electric might just solve the problem

[Skyshadow]

Stop driving 120. 

Not a option! 

[Skyshadow]

It sounds like your vacuum pump is weak/not working.

I think an electric might just solve the problem

That's what I was figuring. What type of pump should i be looking into? I figuring I don't need one that pulls more then just a few PSI.

[ducpainter]

That's what I was figuring. What type of pump should i be looking into? I figuring I don't need one that pulls more then just a few PSI.

Something like this...http://www.davesdiscountautoparts.com/item.wws?mfr=BECK/ARNLEY&sku=152-0568&source=GOOGLEBASE

or this...http://www.lbcarco.com/electric-low-pressure-fuel-pump-fuel-filter-and-elements.htm

or you could go to auto-zone and see what they have.

Some people think a low pressure electric pump will cause float needles to leak.

I think 4 gallons of fuel under atmospheric pressure is stronger than 2.5-4.5 psi.

[Skyshadow]

Either way, As long as the petcock shuts off the fuel, I dont have to worry about leaks.

[ducpainter]

Either way, As long as the petcock shuts off the fuel, I dont have to worry about leaks.

Petcock is only for when the bike isn't running.

[Skyshadow]

Soo, I will have to run a fuel regulator?

[ducpainter]

Soo, I will have to run a fuel regulator?

I don't believe so.

If your float needles are in good condition the 3 ish psi the pump produces is less than than atmospheric pressure.

At least that's my thinking.

[Thermite]

Gasoline will produce .295 psi per foot of depth.  Quantity of gallons does not matter, just the depth.

Since you don't have a full foot of fuel depth a 3 psi pump will be putting more than 10 times the pressure against the float valves as a gravity system.  Since it already has a fuel pump the floats are designed to stop a certain amount of pressure.  Adding more pressure will overdrive the floats and cause fuel to flow when it shouldn't as DP has said.

The 3 psi rating of the fuel pump includes atmospheric pressure but it makes no difference because atmospheric pressure is exerted against the fuel in the bowls also (14.7 -14.7 = 0).  There are gauges that read in absolute pressure pressure but they are for specialized applications and do not apply here.

Not saying it won't work fine but rather just reporting the physics correctly.

C-14

[Skyshadow]

^ I'm not fully sure what your saying here but I believe it means I need a regulator... (Good info though man!)

[Thermite]

^ I'm not fully sure what your saying here but I believe it means I need a regulator... (Good info though man!)

It depends on the output of the original system.  The floats were designed for a specific pressure.  A little less should be okay as they open the needles by losing flotation when the fuel level in the bowl is low.  Too much pressure will force fuel past the needles all of the time.

3 psi is quite low.  I actually think it should be okay.  The part that's missing here is knowing what the output pressure of the vacuum pump should be.

You may be reducing the output of the vacuum pump with the open air box.  If you need to go 120 you may want to consider returning the airbox to OEM spec.

And to those who say you don't need to go 120 

[Skyshadow]

ok, cool. I'm not a fan of the vacuum set up and need to lose it for my next mod anyways so I think I'll go electric with a regulator to be safe.

[ducpainter]

ok, cool. I'm not a fan of the vacuum set up and need to lose it for my next mod anyways so I think I'll go electric with a regulator to be safe.

What pressure are you going to regulate it to?

You don't know for certain that 3 psi is too much...do you?

[Skyshadow]

No, but from Duccutters i know what pressure i need to do what I'm doing.