Click
here for larger view (a)=Needle Length (mm)
(b)=Length between point (x) and the beginning of taper point
(y)
Variables in needles:
- Overall length
- Taper
- Distance from clip position to taper begining.
- Major diameter where it interferes with the needle jet at idle.
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Selection Guide:
Often we are asked what needle to use when an OEM needle is no longer
available. The way Mikuni Needle numberings work is:
The first number is the length series. Lets take the series 4 needle. It could be 40.00-49.99mm in length. In turn a 5 could be 50.00-59.99mm in length.
The second and sometimes third characters being letters describe the taper
from the clip end to the tip in 15minute (1/4th of a degree) increments. For example
"B" is 30 seconds, and "E" is 1 degree, 15 seconds. Therefore a "BE" would be a taper starting out at 30 seconds (1/2 degree), followed by a second taper of 1min 15sec.
The last digit be it one or two characters is the suffix or revision number. Example.
4D3, and 4D8 are the same style needle, similar in length and taper. However the taper may begin higher
up on the needle than the other. This would make a smaller tip diameter, or a shorter needle. If
shims, or clip positions were incorporated on one needle it is possible that it
may effectively perform like the other. For this reason we sometimes suggest
ordering a 4D3, or 4D8 for example if an OEM application calls for a 4D5 which is not
available, instead of a 4E?
Lastly
there is sometimes a number designated by OEM's and this designates the
clip position. Example: 5DP3-4. However this "-#" designation is
not part of the needed part number.
One last note:
A suffix number has the following unknown variables between one needle and another. Exact length, Major OD, Point of begining of taper in reference to clip position. Without physically measuring them there is no way to determine these characteristics just by looking at the part number.
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