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Vacuum fuel pump on 675cc bore

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I just combing there forums to see if anyone has done a vacuum pump kit on there xr's since i have so many engine mods I need the extra fuel boost with return lines.

Here is what one looks like

If anyone has ran one let me know how it went 

will be installing one in the next few days

gy125vacuumfuelpump-500x500.jpg

Edited by whiteXR1

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That's a pump that Polaris uses on a bunch of their ATVs.  I've never heard of anyone using one on their bike though.  It doesn't have a return line.  One port is vacuum pulse, one fuel in from tank, one fuel out to carb.  It is used because the carb bowl sits higher than the bottom of the tank.

I'll say if you actually need one you may be the first.  If your carb is starving for fuel I don't think this should be the place to start looking.  Many people run big bores, and bigger bores, and have never had a fuel rate issue.  Similar petcocks and fuel lines on other bikes supply mutiple carbs and much larger engines without issue.  

If you do add it tell us all about it though.

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I'm also wondering why you feel the need to make that change.  Mine is a 675 and had no problem getting fuel to the carburetor when I spent a minute or two trying to find out what terminal velocity was.  It hit 95 mph and held steady there.  Throttle wide open the whole time.  No fueling issues at all.

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The pump isn't necessary , you've obviously got other issues. They bore and stroke these things to 742 cc's and don't need fuel pumps. Gravity feed is all that's needed as long as the carb is below the fuel tank.

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Really, who told you, you needed a fuel pump?  I've built over a dozen very fast and powerful bikes over the last 30 years.  One in particular was a 1200cc big block 135 HP Kawasaki street bike thst would do 170 mph.  None of these builds needed a fuel pump all were gravity fed.  How in the world would a single cylinder engine putting out 40 HP require a fuel pump?  

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2 hours ago, baldy110 said:

Really, who told you, you needed a fuel pump?  I've built over a dozen very fast and powerful bikes over the last 30 years.  One in particular was a 1200cc big block 135 HP Kawasaki street bike thst would do 170 mph.  None of these builds needed a fuel pump all were gravity fed.  How in the world would a single cylinder engine putting out 40 HP require a fuel pump?  

Well, i thought it would need the extra fuel. I was going through the tuning  and it seems to be running lean top end. Maybe its the tank and pet cock  I'm running (idk). I'm going to install it and will give feed back when done. it seems to be bowls are emptying faster then the gravity can fill them. 

Im not running and electric pump for your info  its like one thats on a shifter carts that is ran off the crank pressure vacuum. 

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:facepalm:   What's your plug look like ? Did you change your exhaust or switch to a different air filter ? Is your petcock or main jet clogging ? Have you ever heard of jetting ?

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The 1997 Ducati Monster had a vacuum fuel pump that worked in a similar fashion.

Pull the fuel hose off of the carburetor and see how much fuel flows out.  If it's a steady stream, it is enough.

Are you sure your main jet is the right one?

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14 hours ago, Hollerhead said:

That's a pump that Polaris uses on a bunch of their ATVs.  I've never heard of anyone using one on their bike though.  It doesn't have a return line.  One port is vacuum pulse, one fuel in from tank, one fuel out to carb.  It is used because the carb bowl sits higher than the bottom of the tank.

I'll say if you actually need one you may be the first.  If your carb is starving for fuel I don't think this should be the place to start looking.  Many people run big bores, and bigger bores, and have never had a fuel rate issue.  Similar petcocks and fuel lines on other bikes supply mutiple carbs and much larger engines without issue.  

If you do add it tell us all about it though.

Im going to install and let you know the out come. Their is methods on installation to make a return line so the bowls don't flood when the  bike is at idle. i know from shifter cart experience  it gives a 3 times better throttle response with no lean conditions. 

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What they said, the fuel pump idea is a waste of time and money.  Find your problem and fix it avoid fixing the symptom.

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2 minutes ago, ScottRNelson said:

The 1997 Ducati Monster had a vacuum fuel pump that worked in a similar fashion.

Pull the fuel hose off of the carburetor and see how much fuel flows out.  If it's a steady stream, it is enough.

Are you sure your main jet is the right one?

yea my main jet is 175 and  the fuel petcock is a stead stream. But keep in mind i have port polish,  larger valves ,3angle  job,  stage one cam , and port flow on the head. and it still bogs a little bit when I'm cruising and then i hit the throttle WOT.

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3 minutes ago, baldy110 said:

What they said, the fuel pump idea is a waste of time and money.  Find your problem and fix it avoid fixing the symptom.

that fuel pump is only 25 buck and it a simple fix for constant power.

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I think your floats just out of adjustment to be honest if it's emptying out too fast. An electric pump is overkill

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2 minutes ago, Brad04 said:

I think your floats just out of adjustment to be honest if it's emptying out too fast. An electric pump is overkill

their is no adjustment with the oem carb 

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Just now, JoeRC51 said:

A pump will be useless.

i will find out. tomorrow.  if not different tank. 

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8 minutes ago, whiteXR1 said:

yea my main jet is 175 and  the fuel petcock is a stead stream. But keep in mind i have port polish,  larger valves ,3angle  job,  stage one cam , and port flow on the head. and it still bogs a little bit when I'm cruising and then i hit the throttle WOT.

Yeah so what so does mine and I'm running the stock carb with a 155 main jet and it runs great.  

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6 minutes ago, JoeRC51 said:

 

 

18 minutes ago, JoeRC51 said:

:facepalm:   What's your plug look like ? Did you change your exhaust or switch to a different air filter ? Is your petcock or main jet clogging ? Have you ever heard of jetting ?

i have full exhaust , K&N filter and the jetting is almost max out for the OEM carb and  my plug looks a little too clean for  top end 

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