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HD8 Carburetor Float Arm Setting

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Goldie

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I just replaced my shut off valves in my HD8 carbs. They have a small spring loaded tab on the bottom. When I set the 7/16 clearance should I depress the tabs.The old valves did not have the spring tabs. I have watched several youtube videos on the clearance adjustment but none showed the type I now have.
 
I thought about this for a long time myself. Since the valves won't close until the springs compress that's where I set them. I believe the spring-loaded tabs (pistons?) are there to damp float movements, hence why some have them and some don't.
 
Bob_Spidell said:
I thought about this for a long time myself. Since the valves won't close until the springs compress that's where I set them. I believe the spring-loaded tabs (pistons?) are there to damp float movements, hence why some have them and some don't.
Click to expand...
I have watched Joe Curaco(sp?) Video on fuel bowls and I could not see any mention. Even watched a youtube on Jag HD8 carbs but that style valve was not mentioned.
 
Goldie--

Where did you buy them?
 
I just had the same question, and found a consensus that the spring plunger should not be compressed - they should be set when the spring loaded tip just touches the arm.


Here is the Google AI Overview

When setting the float height on an SU carburetor equipped with a spring-loaded needle (often called a "plunger" or "cushion" needle), the tab on the float lever should just touch the end of the pin, without compressing the spring. [1, 2]
  • The Correct Method: Hold the carburetor bowl lid vertically, so the weight of the float hinges down and puts minimal pressure on the needle.
  • The "Just Touching" Point: The tab should be adjusted until it merely makes contact with the plunger. The spring should remain fully extended. [1, 2, 3, 4, 5]
Why Not Compress the Spring?
Compressing the spring during measurement will cause you to set the float too high, resulting in a fuel level that is too high, leading to over-fueling, stalling, or flooding. [1, 2, 3, 4, 5]



This was also reported by John Twist MG Tech of University Motors.
 
That's what I actually did but was concerned i had set it incorrectly. I have driven the car and it does not overflow and runs great.
 
That makes sense (too). The other factor is I think you want the float arm level--i.e. parallel to the bottom of the lid--to prevent the plunger from getting jammed in the valve body.
 
I missed your question earlier and have been off-line a while. I bought the HD8 carb parts from Moss. I have bought a few things from AH Spares but not the carb parts. The tips of the needle valves have some sort of coating on them and a spring in the bottom. I have some others that I have not installed in my spare parts bin that do not have the little spring loaded bottom. I had to do some adjustment on the finger assembly to get it positioned correctly 7/16". When I turned the top of the float bowl over, one finger assembly would hang too low. Had to work on the little fingers at the hinge so it would hang more level.
 
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