Setting float level on a KX250, help please

[thirtyfour]

the bike is a 01 KX 250
the bike already has a smaller (155 main ) and smaller (48) pilot jet, yet it is fouling plugs like crazy.
I am suspecting that the cab flat may not be set correctly.
with the bowl removed if I turn the carb upside down the float is NOT level with the housing, it sits deeper.
my question about setting the float,
the fuel shut off valve seems to have a smaller valve or some rod/plunger inside(about the size of a wrist pin bearing needle), may be used for dampening the float action.?
Do you set the float level with this smaller rod pushed in, or its normal (sticking out) position?

also my previous KX had a white plastic piece placed over the main / pilot jet area , tis carb does not have such thing..
what would be its purpose?
thanks for your help.

 

[Morvo]

On my KX250 1995 model the float height should be between 14mm and 18mm. If it is out of this range then the way to adjust it is to:

1. Remove the carb
2. Remove the float bowl chamber (4 screws)
3. Set the carb upside down but at an angle so the float valve arm doesn't compress the needle valve
4. Whilst holding the fuel valve seat down measure the distance from the gasket base (where the float bowl chamber screws onto) and the top of the float.
5. If the float height is out of the specified range as mentioned above then remove the float assembly (remove pin and valve), and bend the arm where the fuel valve hangs off from either up or down, depending on what your measurement was.
6. Re-measure the float height again and adjust again if neccessary.
7. Re-bolt the whole carburetor back together again and try it out!

 

[Faded]

On my KX250 1995 model the float height should be between 14mm and 18mm.

That is a huge spec. They are usually listed in one mm dimension and vary +/- 0.5mm.

Float level is a maintenance item, should be checked/set at regular intervals. Not sure on the spec for your bike, but here's the how-to;

You’ll need to first start off by removing your carb. Be sure to clean the surrounding area to the best of your ability to avoid dirt and debris falling into your carb, or worse, your engine. After you’ve removed your carb I would suggest a thorough cleaning using carb cleaner (or equivalent) and compressed air to ensure that all jets and passageways are spotless. Avoid using wire or other tools to clean orifices of jets; it’s all too easy to alter their original designed dimensions.

After your carb is clean you can now set your float level. The picture below will allow you to become familiar with the parts that are responsible for maintaining the correct float level in your carb. There are four basic parts, the floats themselves (part of the float assembly), the float assembly tang, the fuel inlet needle valve, and the fuel inlet valve seat.


Float Level Pic #1
(Float assembly pivot pin not shown.)


It is always a good idea to remove the float assembly pivot pin (already shown removed) and extract the float assembly and the fuel inlet needle. The fuel inlet needle is a wearable part and over time can deteriorate. A worn fuel inlet needle can contribute to an irregular float level. Most fuel inlet needles consist of an internal spring loaded bumper (which contacts the float assembly tang) and a plastic or Viton (rubber) tip. Inspect the fuel inlet needle tip for wear and/or damage. To give you an idea, Eric Gorr recommends replacing the fuel inlet needle/seat assembly every two years. The average cost is around $15-20.


Float Level Pic #2
(Fuel inlet needle shown with Viton (rubber) tip. The Viton is used to isolate the fuel inlet needle from vibration and to create a better seal against the fuel inlet valve seat.)


Now that you’ve made sure you aren’t going to have any issues from worn parts you can reinstall your needle, float assembly and float assembly pivot pin and continue on to set your float level. The float level measurement is taken from the top of the floats (when the carb is positioned upside down) to the gasket surface of the float bowl as illustrated in the next picture. You can use an open-end wrench (sized per your spec), a small metric ruler, or a float level gauge. The tolerance for your float level is usually around +/- 0.50mm.


Float Level Pic #3


When setting the float level be aware that the spring loaded bumper on the fuel inlet needle valve may have a tendency to compress under the weight of the float assembly which will skew your measurement. Before you obtain your measurement you’ll need to make sure that the float assembly tang just barely makes contact with the spring-loaded bumper. Sometimes it is easier to hold the carb body at a 45-degree angle to avoid compressing the spring in the fuel inlet needle.


Float Level Pic #4


If you find that your measurement does not match your float level spec then you can carefully bend the float assembly tang to achieve your desired measurement. Be sure to recheck your work, and if you feel confident that your float level is spot on then you can reinstall your carb and get back to riding.

 

[thirtyfour]

Thank you very much for the replys,
the one with the pictures are very usefull.
I was not sure if the spring loaded bumper needs to be compressed or not ,
as you said the weight of the float would over come /compress the internal spring.
I managed to look up specs for the 01 KX 250
it is : 6.5mm+/-1 from the top of the float to the carb base

now the picture is complete
thank you

 

[mattb348]

That is a huge spec. They are usually listed in one mm dimension and vary +/- 0.5mm.

Float level is a maintenance item, should be checked/set at regular intervals. Not sure on the spec for your bike, but here's the how-to;

You’ll need to first start off by removing your carb. Be sure to clean the surrounding area to the best of your ability to avoid dirt and debris falling into your carb, or worse, your engine. After you’ve removed your carb I would suggest a thorough cleaning using carb cleaner (or equivalent) and compressed air to ensure that all jets and passageways are spotless. Avoid using wire or other tools to clean orifices of jets; it’s all too easy to alter their original designed dimensions.

After your carb is clean you can now set your float level. The picture below will allow you to become familiar with the parts that are responsible for maintaining the correct float level in your carb. There are four basic parts, the floats themselves (part of the float assembly), the float assembly tang, the fuel inlet needle valve, and the fuel inlet valve seat.


Float Level Pic #1
(Float assembly pivot pin not shown.)


It is always a good idea to remove the float assembly pivot pin (already shown removed) and extract the float assembly and the fuel inlet needle. The fuel inlet needle is a wearable part and over time can deteriorate. A worn fuel inlet needle can contribute to an irregular float level. Most fuel inlet needles consist of an internal spring loaded bumper (which contacts the float assembly tang) and a plastic or Viton (rubber) tip. Inspect the fuel inlet needle tip for wear and/or damage. To give you an idea, Eric Gorr recommends replacing the fuel inlet needle/seat assembly every two years. The average cost is around $15-20.


Float Level Pic #2
(Fuel inlet needle shown with Viton (rubber) tip. The Viton is used to isolate the fuel inlet needle from vibration and to create a better seal against the fuel inlet valve seat.)


Now that you’ve made sure you aren’t going to have any issues from worn parts you can reinstall your needle, float assembly and float assembly pivot pin and continue on to set your float level. The float level measurement is taken from the top of the floats (when the carb is positioned upside down) to the gasket surface of the float bowl as illustrated in the next picture. You can use an open-end wrench (sized per your spec), a small metric ruler, or a float level gauge. The tolerance for your float level is usually around +/- 0.50mm.


Float Level Pic #3


When setting the float level be aware that the spring loaded bumper on the fuel inlet needle valve may have a tendency to compress under the weight of the float assembly which will skew your measurement. Before you obtain your measurement you’ll need to make sure that the float assembly tang just barely makes contact with the spring-loaded bumper. Sometimes it is easier to hold the carb body at a 45-degree angle to avoid compressing the spring in the fuel inlet needle.


Float Level Pic #4


If you find that your measurement does not match your float level spec then you can carefully bend the float assembly tang to achieve your desired measurement. Be sure to recheck your work, and if you feel confident that your float level is spot on then you can reinstall your carb and get back to riding.

Very good information here, and greatly appreciated!

I have been wondering how to set the float level for awhile now, and you have just answered ALL of the questions I had about it. Thanks again.

 

[Faded]

No problem. I'm glad you guys were able to use it. :cool:

Take care,
Andrew