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Discussion Starter #1
Hi guys, I've read everything I can find and loads of people's opinions on this topic but honestly unless someone has done it they can spout all the opinions they want. It'll either work or it won't. So on that token I've a gen 1 that is running like a missile. Until it's above the 95 mark for longer than 30 secs then I start to get fuel starvation. This thing is jetted with full system, cams and a couple of other bits and bobs. I'm trying to find out has anyone actually fitted an aftermarket electric fuel pump to one. I was looking at the pump from the old cbr250 but I'm concerned that the flow will not be enough. It's rated for 3 to 5 psi which is about right but the flow concerns me. Now I have already swapped the mechanical pump for a new one and it did improve but it's still not enough. This is why I'm looking to find someone who has done this and can say definitively that a certain pump will work. I appreciate your input guys any help is appreciated.

On a separate note I'm also after an online 12v cut off solenoid to do away with the poxy vac tap as I'm already running one of my other projects straight flow from the tank.

On the other hand if the recommended pump has a positive fuel cut off it may suit me to fit one on each and do away with both the taps.

Again thanks guys this site is a trove of info that has saved me loads of times but on this one please tell me it's been done or I may cry.... Lol
 

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Fuel starvation at 95 is not due to the fuel pump. Maybe check the tank venting. Or it might be jetted too rich and starts fuel fouling after extended time at full throttle.

The gen1 SV650 carburetors are gravity fed, no pressure needed.

The very bottom of the SV fuel tank is lower than carburetor bowls, the only thing the fuel pump does is scavenge the last bit of fuel when the fuel level drops below the float bowls.

So long as there is more than, say, 1/4 gal of fuel left in the tank, the gen1 SV will run fine even if the fuel pump were to be bypassed.
 

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Discussion Starter #4
In general The needle height affects the midrange not the top end. The top end is governed by jet size mainly. And while I get where your coming from teeriver trust me is starving out at the top end. I've done a plug chop when it acted up it's the rear carb is running dry. We've ran it with an aux pump from a cbr 600 (the cbr pump caused it to flood low down though) on a switch to prove it. This is why I'm looking for a pump that can be used permenantly. I probably should have said that already. I was just fit to set a match to it when I asked the question.
 

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I hear you, Cragybar, but all carburetors that use floats for fuel level are gravity-driven. If adding pressure to the fuel line makes the bike run better then the jetting is wrong or the carburetor is dirty/broken. An auxiliary pump is not the answer.

Have you inspected the fuel petcock? A clogged screen there might be limiting fuel flow.
 

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Discussion Starter #6
I get your thinking mate but it's not pressurizing the carbs it's filling the bowls before they run dry and if sv's didn't need a fuel pump suzuki wouldn't have ever fitted the vacuum opperated one that is on there from factory. It cannot keep the bowls full enough to run the bike. Float heights are set carbs are synced and it runs fine. The petcock is brand new genuine suzuki. I have ran this bike directly from an adapter on the fuel gauge point with an additional inline pump and a 1 way valve. The second it shifts the extra fuel into the carbs it runs fine again. For a few secs till you run the pump for an 3xtra sec. If this was a track bike I'd leave it on fulltime as it would never see the bottom end of the revs but it's not so I can't exactly set tick over at 5k lol.

On a separate note how does the sv run with a 2 into 2 single pipes system for track? Does it make much difference. I have a 2 into 2 with collector pipe but it's on its last legs and it would be very easy to cut and patch as 2 separate pipes. I have too much time at the moment with this lockdown.
 

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Dear Cragybar,
You are meowing up the wrong catpost. The carburetors on the SV650 are gravity-fed, no fuel pump required. The only reason for the fuel pump is to scavenge the last bit of fuel from the tank when the level falls below the carburetor bowls. Other than that there is no need for the fuel pump. You can bypass the pump completely, throw it in the trash. The only thing you would lose is a little tank capacity.

Even at full throttle, max load, there is only a small trickle of gas flowing to the carbs. The only way a fuel pump would be necessary is if the float valves were hanging full open and still starving for fuel. So long as your tank is clean and the petcock screen is clean, gravity provides more than enough fuel volume.

Adding an extra fuel pump to your SV650 will not solve the problem. Most likely, the carburetors are not setup properly.

57019
 

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Discussion Starter #8
The floats in the carbs control the needle valve which keeps the bowls of the carbs full.(or rather at the correct level ) it's like a tap. If the fuel level drops the fuel is not at the correct level and the valve opens to allow extra fuel into the bowl. The jets and needle are what controls the fuel flow into the engine. I'm not looking to pressurize the fuel through the jet. Merely ensure that the fuel level remains at the correct hight in the bowl. Hense asking about fuel pump from and old cbr etc as they run at about 3 to4 psi this is enough to fill the bowl but not enough to over pressure the lines and bypass the needle valve on the float.

Manuals are written by engineers with degrees based on the machine as it came from the factory not one that is completely modified. Mechanics have been fixing stuff that engineers got wrong for years. So just cos the manual says something it's not gospel.

I know that a standard bike will run fine with no pump but then again so would an old cbr600f1 , f2 until you add an exhaust , k&n filter, do a little head work and thrash the life out of it, then you need the pump or it runs lean. The yamaha fzr400 was the same story. The reason that the bike runs as well as it does is due to the size of the float chamber and the fact that it can hold as much fuel as it does. It is compensating but just not quite able to keep up. The fuel pump is basically acting as a transfer pump. From the tank to the bowls.
 

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Sorry, no. There are no engine mods that would require an auxiliary fuel pump for the gen1 SV650.
 

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I get your thinking mate but it's not pressurizing the carbs it's filling the bowls before they run dry and if sv's didn't need a fuel pump suzuki wouldn't have ever fitted the vacuum opperated one that is on there from factory. It cannot keep the bowls full enough to run the bike. Float heights are set carbs are synced and it runs fine. The petcock is brand new genuine suzuki. I have ran this bike directly from an adapter on the fuel gauge point with an additional inline pump and a 1 way valve. The second it shifts the extra fuel into the carbs it runs fine again. For a few secs till you run the pump for an 3xtra sec. If this was a track bike I'd leave it on fulltime as it would never see the bottom end of the revs but it's not so I can't exactly set tick over at 5k lol.

On a separate note how does the sv run with a 2 into 2 single pipes system for track? Does it make much difference. I have a 2 into 2 with collector pipe but it's on its last legs and it would be very easy to cut and patch as 2 separate pipes. I have too much time at the moment with this lockdown.
Anecdote: My mates 1st gen SV with stock vacuum powered pump that I rebuilt myself goes down the mile long front stretch at PIR hitting over 130mph before having to slow down. I put big jets in his carbs. Sorry I don't recall the size.
 

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Have the carbs been correctly balanced?

Check here,

 

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I have had (not on a sv carb yet) needle valves that don't open fully. Could be corrosion, dirt or mal adjusted float
When the fuel level drops in the float bowl they may open supplying fuel but not enough for sustain high load.
Best fit new needle valves and check the float drops enough so they are fully functioning.
 

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Dear Cragybar,
You are meowing up the wrong catpost. The carburetors on the SV650 are gravity-fed, no fuel pump required. The only reason for the fuel pump is to scavenge the last bit of fuel from the tank when the level falls below the carburetor bowls. Other than that there is no need for the fuel pump. You can bypass the pump completely, throw it in the trash. The only thing you would lose is a little tank capacity.

Even at full throttle, max load, there is only a small trickle of gas flowing to the carbs. The only way a fuel pump would be necessary is if the float valves were hanging full open and still starving for fuel. So long as your tank is clean and the petcock screen is clean, gravity provides more than enough fuel volume.

Adding an extra fuel pump to your SV650 will not solve the problem. Most likely, the carburetors are not setup properly.

View attachment 57019
there is no fuel pump on a Gen 1. mine tops at about 135-140 at Daytona. no starvation. fuel screen could be plugged, tank vent too small, but you need no fuel pump.
 

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there is no fuel pump on a Gen 1. mine tops at about 135-140 at Daytona. no starvation. fuel screen could be plugged, tank vent too small, but you need no fuel pump.
There is a fuel pump on the gen 1 sv650 as per the diagram supplied by TeeRiver
 
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