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Old December 30th, 2018, 12:46 AM   #10
DannoXYZ
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Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011

Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C

Posts: A lot.
MOTY - 2018, MOTM - Nov '17
Quote:
Originally Posted by maverick9611 View Post
i agree, i was on the jetting merry go round till danno yanked me off it. i will dropping to 95's too. 98 is ok but i want it all.
Don't do it! With factory needles, there's lean spot from 6500-8000rpms as seen on dyno-chart above. Going with smaller mains to lean out top-end will cause stumbling in mid-range. Sure shimming needles will help, but will also richen top-end and negate effects of downsizing mains. Back in '80s, I used to grind custom needles on mini-lathe to cure this issue. Nowadays, i just install EFI. However, there is in-between solution:



Leftmost purple vertical-line is needle in jet at closed position.
Middle purple vertical-line is needle in WOT/high-rpm position.

#3 = factory stock New-gen needle
#4 = DynoJet stage-2 needle

Notice DynoJet needle has larger diameter tip than stock with slightly thinner middle? Compared to stock, this leans out high-end while adding fuel to mid-range. This needle along with DynoJet-94/Keihin-95 mains should give you optimum AFR for max-power.

Start with richest clip-position (lowest) for richest mixtue. Need to use wideband or dyno to measure actual AFR (WOT 4th-gear), should around 12:1 in high-end. Lean out mixtures to 12.5-13.0:1 by raising clip one position at time. This will be optimum for street bike while giving you safety margin for bad fuel. Max-power is a little leaner, but extra 0.5hp isn't worth it unless it's race-bike.
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