Carb needle washer mod

Ok all you needle-washer modders out there, I need a little help making sense of this procedure.

As I understand it, the aim is to raise the needle in it's seat in the 'at rest' position, to allow more fuel to be inducted. This is achieved by inserting a washer underneath the needle' 'head'.

Now, my problem is this. Using the recommended #4 SAE washer, it seems to me that the outside diameter of the washer prevents the needle from dropping right down to its normal seating position, due to the 'stepped' nature of the bore that holds the needle.

#4 SAE washer (outside diameter 13 mm)

Normal position of needle, seated at bottom of chamber.

Needle plus washer, seated at bottom of first 'step'

So, my question becomes:

"is this the correct outcome intended by this modification, or is the real intention to raise the needle by the width of the washer?"

If its the latter, then clearly I'm using the wrong washer, and need one whose outside diameter matches the diameter of the head.

How does this compare with the modification others here have done?

 

CB900FA
TOP