 Go to any of these pages to see their listings of needles: Mikuni VM/TM Carbs Mikuni TMS/TMX Carbs Keihin Carbs Dellorto Carbs Low Throttle Jetting This is controlled by 1) how open the throttle is when the beginning of the needle taper is at the top of the needle jet. Normally this is around 1/4 slide open (not 1/4 throttle). 2) the clearance area between the straight section of the needle and the needle jet. Over decades the needle jet gets wallowed out and either needs to be replaced or the needle has to be changed for a fatter one (if possible. Not possible with Mikuni VM). 3) the slide cutaway height. Higher is leaner. You can make it lower by cutting grooves in the lower slide there and putting on JBWeld. 4) after 1/4 slide open the jetting is controlled by the needle taper. More angle there makes it richer. 2 and 3 taper needles often make this portion too lean. I prefer single taper needles. Mid Throttle Jetting If jetting is too rich at mid throttle then you need a leaner needle (one with less taper angle). Too rich gives inconsistent exhaust sound and loves it when you crack the throttle open. If jetting is too lean at mid throttle you need a richer needle (one with more taper angle). Too lean hates it when you crack the throttle but has a consistent exhaust sound. Test it by riding at partial throttle for steady speed and note the exhaust sound and then crack the throttle open. WOT Jetting This is a combination of the needle taper and the main jet. I know the jetting charts show the main jet as fully in charge. They are over-simplified for the low IQ motorcycle crowd. This is the only correct jetting chart:  |