Question about 1987 Yamaha FZR 250

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Fuel pump and overflow

My fuel pump turns on but the carbs over flow i cheacked te carbs but could not find the flaw some times it over flows some times it does not
and plz can some one guide me where can i get a complete set of carburator and a new fuel pump i need it for the fz250 and fzr250 phazer both yamaha

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  • westwind19_2 Dec 25, 2008

    mannnn u made my day i was stuck with the problem for a month i tried it on 1 off the carbs it worked only 3 were overflowing then i tried it on the rest it worked thanx for saving my money thanx a lot u r realy a guru do tell me if u now where can i get spares for the fz 250 phazer toooo it will be a great help

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The problem is not so major. There are a couple of things you need to check.

  1. Make sure you are not getting dirt in the system because it will cause the "needle and seat" to not seal properly when the float chambers are full.
  2. Reset the float level. In time the "needle and seat" in the carbs wears and consequently you will need to reset the float level. You can contact me if you cannot find the float specs and I'll tell you how to do it without elaborate measuring equipment. It's sort of complicated to explain but easy to do.
  3. Worse case scenario you will need to replace the "needle and seats" in the carbs. They come as a unit sold separately so you will need one for each carb.
  4. You do NOT need to replace the carbs. DO NOT go buy a new set, you're wasting money. The fix is really quite simple and at a fraction of the cost if any.
My experience tells me that you should almost be able to simply readjust the float level to cure the problem. The needle and seat will endure up to 12.5 lbs of fuel pressure minimum so not to worry.
Best of luck and let me know if you need further assistance.
Regards,
RSelvy

Posted on Dec 19, 2008

  • Rob Selvy
    Rob Selvy Dec 26, 2008

    I'm very glad I was able to help you. I'll do some checking to see if I can find a parts outlet for you.
    Good luck in the future and remember to seek your answers here first before you go and spend money elsewhere. FixYa.com gives pretty good advice.


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1 Answer

Why is my carburetor leaking fuel after I turn off my motor


It is most likely that your shut off valve is leaking (as fuel flow should be shut off with no vacuum applied to it). If the float level is okay, and it must be set very precisely at 0.413 - 0.453 inches with the carb tilted no more than 20 degrees and no less than 15 degrees, (if the float level is the problem such that the fuel supply would be too high in the float bowl and depending on how far out it is set ie how high the fuel is allowed to rise in the float bowl it would likely be leaking out the overflow and not the carburetor itself). As unlikely as it would be to have fuel flowing out the accelerator pump circuit and discharge port you would easily be able to identify such a leak by seeing it flow out of the accelerator pump discharge port in the front part of the carb throat. If the needle and seat are not sealing and fuel flow was available from the shut off valve as it should not be with no vacuum applied to it then it would not matter that the float level was set correctly because it would continue to flow past the needle ans seat when the float had risen to the proper shut off point. In this case it might leak out of the main discharge port before the level became high enough for it to leak out of the overflow or it might leak out both. It is doubtful that a defective enrichener would cause a leak because the fuel would have to rise to high to emerge from the enrichener discharge ports. It might leak out the off idle discharge ports but these are behind the venturi piston and the butterfly valve so you would have to raise the former and open the latter to see if fuel was emerging from these ports. I have not dealt much with H-D CV carbs but my understanding of them leads me to suggest the above. SO, a leaking carb with the engine shut off is most likely to be a result of a defective fuel tank valve so first remove the fuel hose from the shut off valve and see if there is fuel draining from the nipple at the valve or if you take it off at the carb if there is any fuel leaking out of the fuel line you removed from the carb.....There should be no fuel flow with the engine off and no vacuum. If there is no fuel flow here there should be no fuel flow from the carb unless the float level is out and the fuel level in the float bowl has risen too high before the fuel valve shut of fuel flow. Even so the fuel leak should not be continuous but only as much as there was fuel in the fuel line and carb downstream of the shut off valve. If the leak is continuous you know the valve is the first problem and then you also have a float level setting that is out allowing too much fuel into the float bowl and/or the needle and seat are not sealing and shutting off the flow when the float rises to the proper shut off height. Or, you could have a gasket leak at the float bowl. If there is no fuel flow from the fuel shut off valve and the float level is correct there likewise should be no flow from the accelerator pump (or any other circuit) because the fuel level would never be high enough to flow out the discharge the accelerator discharge or other ports. Remember that the accelerator pump check valve only operates when the fuel is being forced out of the accelerator pump circuit ie the valve does not stop or control fuel flow into the accelerator pump diaphragm area, it only stops flow back to the float bowl area when fuel is being pressurized to force fuel up and out the discharge port. I hope this helps somewhat in diagnosing your leak.

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Hello
Your gas tank petcock is diaphram operated.
there is a vacuum line coming off the intake, that goes straightb to the petcock.
when you turn the motor over a vacuum is created, pulling the petcock diaphram back and allowing fuel to flow to your carburetor. when you turn the motor off the vaumm is gone and the spring behind the diaphram pushes it closed and stops the fuel flow to the carbs.

Now the reason the carbs are overflowing is because the floats valves are not closing, in other words the floats are sticking.
Usually a good carb clean will cure the problem, especially for that year.
the older ones usually require new float valves/seats that are usually found in a good carb rebuild kit. You shouldn't need one.

If your really broke try tapping on the bowls of the carburetor lightly, while the engine is running, sometimes the vibration will vibrate a particle loose that may be holding open the float valve.
if it works then the fuel should stop overflowing while running.

if you know how to work on it, try this, with the engine off.
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get a container to catch the gasoline.
while fuel is flowing tap the carb bowls a few times then closed the drain screws.
clean up any spilled gasoline .
start your bike.see if they stop leaking and the floats are closing.
if it still leaks, you'll need the cleaning.

Happy Riding
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1 Answer

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1 Answer

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1 Answer

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1 Answer

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Hi and welcome to FixYa,

Initially, to your queries:
  • hook up all the vacuum lines - yes or cover/plug all
  • to stop fuel flow - hooking up all the vacuum lines or covering/plugging them would be technically correct but will not stop the flooding/fuel overflow;
  • run correctly - with constant overflow/flooding, it will not run correctly.
To my knowledge, overflow could only be caused by:
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  • dirt, sand, foreign object lodged against inlet port hole;
  • mis-adjusted floats;
Which would mean, go to do it all over again.

Just a start, do postback how things turned up or should you need additional information. Good luck and Thank you for using FixYa.

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