okay so im following the tuning manual and setting the float level bending the little brass plate that shuts the needle valve, only thing is that when the carb is upside down the float , set at the right height, and on its own weight only, it does not shut the needle valve, to achieve this the float needs a little extra push down to do that i.e lower than the recommended height in the service manual. i have an overfueling problem and im wondering just how critical the needle valve/float. is it imperative for the float mechanism to actually close the needle valve at the designated height,if its not shutting off until the float is a tad higher (which im assuming must be happening) could this manifest in overfueling ?
Hif44 Float & Needle Valve Question
Started by
kaise7
, Aug 19 2012 09:43 PM
3 replies to this topic
#2
dklawson
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Posted 19 August 2012 - 10:02 PM
Yes to just about all your questions.
The float valve needs to fully close or you are likely to have flooding at idle.
If the valve is not closing and it is new, look for debris that has somehow found its way into the seat. Old rubber fuel lines have been known to cast off debris that causes that. If the valve is new and the seat is clean, inspect the movement of the needle in and out of the seat. There have been reports of some needles "catching" as they move in and out of the seat. The fix has been to deburr the sides of the needle by scraping the "corners" with a pocket knife. You are not trying to whittle away the brass, just smooth the corners a bit and remove any high spots.
If the float valve is old, remove and inspect it. If it is a metal tipped needle look for ridges and rings formed onto the conical tip. If present, replace the needle valve. If the tip is rubber and it doesn't seal, the rubber is probably too old and hardened and it is time for a new valve assembly.
If the needle has a metal tip without rubber and there are no blemishes on the conical tip, you MAY get by through lapping the needle and seat together. People on this board have previously recommended that lapping be carried out by applying a bit of toothpaste to the tip of the needle and twisting the needle about when inserted into its seat. Obviously wash out the toothpaste when done.
If you buy a new float valve I advise against buying "Grose Jets" which use ball bearings to create the seal. I have never had good luck with those and consider them expensive mistakes. The Viton tipped needles have always worked much better for me.
The float valve needs to fully close or you are likely to have flooding at idle.
If the valve is not closing and it is new, look for debris that has somehow found its way into the seat. Old rubber fuel lines have been known to cast off debris that causes that. If the valve is new and the seat is clean, inspect the movement of the needle in and out of the seat. There have been reports of some needles "catching" as they move in and out of the seat. The fix has been to deburr the sides of the needle by scraping the "corners" with a pocket knife. You are not trying to whittle away the brass, just smooth the corners a bit and remove any high spots.
If the float valve is old, remove and inspect it. If it is a metal tipped needle look for ridges and rings formed onto the conical tip. If present, replace the needle valve. If the tip is rubber and it doesn't seal, the rubber is probably too old and hardened and it is time for a new valve assembly.
If the needle has a metal tip without rubber and there are no blemishes on the conical tip, you MAY get by through lapping the needle and seat together. People on this board have previously recommended that lapping be carried out by applying a bit of toothpaste to the tip of the needle and twisting the needle about when inserted into its seat. Obviously wash out the toothpaste when done.
If you buy a new float valve I advise against buying "Grose Jets" which use ball bearings to create the seal. I have never had good luck with those and consider them expensive mistakes. The Viton tipped needles have always worked much better for me.
#3
kaise7
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Posted 19 August 2012 - 10:13 PM
cheers ive been getting sooting up at idle,this may be the answer.thanks.
#4
Ethel
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Posted 19 August 2012 - 10:57 PM
The valve doesn't have to close under the weight of the upside down float, when it's floating the weight of the fuel displaced by the float is pushing it shut. Admittedly it's not much more.
The fuel pump pressure also plays a part as that what the needle valve is holding back, usually only an issue if using uprated (electric) pumps.
The fuel pump pressure also plays a part as that what the needle valve is holding back, usually only an issue if using uprated (electric) pumps.
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