All 4 series needles available direct through the Mikuni Factory are listed on the sales drop down list. Needles not shown will only be available directly through the bike manufacturer for whom they will have been a specially made unique item or they are otherwise obsolete.
IMPORTANT TUNING CHARACTERISTICS
The Jet Needle is the tapered rod that is positioned in the throttle valve by the ‘E’-Clip. The taper of the needle increases the clearance between the Jet Needle and the fixed Needle Jet outlet as the throttle is opened. As the air flow volume increases past the throttle slide, the fuel volume is also increased to maintain the correct air/fuel ratio.
NEEDLE ‘E’-CLIP POSITION
The position of the ‘E’-Clip in the Jet Needle is used to correct or change the air/fuel ratio between 1/4th and 3/4th throttle valve position. The ‘E’-Clip can be raised or lowered on the Jet Needle. To richen the fuel mixture the ‘E’-Clip is lowered on the Jet Needle, raising the Jet Needle. To lean the fuel mixture the ‘E’-Clip is raised on the Jet Needle.
The chart below showing dimensions of some 4 series needles may be of assistance in determining alternative options. See the related measuring points picture in the product gallery.