ATTENTION! This needle reference was produced quite a number of years ago now. Way before we had the new breed of rubbish fuel with ethanol in it. Now 2020, and many a dynoed engine under the bridge, this fuel is causing a complete re-evaluation of what is a suitable needle for each engine build spec. However, until a well researched new set of needle options can be offered up, the below are still reasonable starting points, but would suggest running the just possibly a little lower than usual. Not ideal as this affects idle fuelling as well, but as I said - a starting point. 

 

Unfortunately I cannot give an all-encompassing table of what needles are needed for which engine builds. My life's collection of all the automotive-orientated work I'd ever done was stolen out of my car by some low-life scum a few years back. Not for what it was - but for what it might be. All I have is a few scribbled notes, the source of where I start now. Being an oft-voiced question on the message board, I thought I'd share it with you. Since there is already a very good source of starting points/applications for fixed needle carbs, this is for those floundering about in the wilderness that is the biased (swinging) needle example of the breed. 

 

These are based generally on 1275cc+ motors, using a reasonably modified head, compression ratio on the sane side for unleaded road use, and uses Kent Cam profiles as the main guide so just select one that near-matches what you're using 

 

Std filter case K&N Cone or 

With K&N filter Pancake filter 

Single 1.5" 

MD256 AAK AAU 

MD266/7 AAA AAM 

MD286 AAM ABY 

 

Single 1.75" 

MD256 BDL or BAK BDK 

MD266 BDK BCE 

MD276/286 BBC BBC 

MD296 Modified BBC…………… 

 

Twin 1.5" (assuming K&N pancakes or no filters) 

MD256/266 AAV 

MD276 AAA 

MD286/296 AAM or ABY (ABY is richer towards top end). 

 

Other references - 

These are for comparison and are arranged going from leanest to richest. Makes a good visual example of what happens where on the needle profile in accordance with engine specification when the profile list of each is lined up in a row. 

BEJ - standard unleaded Metro. 

BER - 1.3 Pre-injected Cooper (basically MG Metro spec engine). 

BFA - Alternative Metro Turbo needle, has richer cruise section, but leaner top end. 

BDD - Metro Turbo standard needle. 

BFY - 1.3 Pre-injected Cooper unleaded (basically MG Metro spec engine). 

BDL - MG Metro standard needle. 

BCE - Popular modded engine needle (see above table). 

BBW - 1.3 Pre-injected Cooper with Stage One kit using K&N cone/pancake filter. 

BDK - 1380 fast road spec (MD286, modded head, etc.). 

 

NOTE: 

When choosing a different needle, select one with the same idle figures. If this is not possible, remember - 

If new needle has a leaner idle figure, the rest of the needle will give a slightly RICHER mixture than the profile suggests. 

If new needle has a richer idle figure, the rest of the needle will give a slightly LEANER mixture than the profile suggests. 

This is caused by re-positioning of the jet to get correct idle mixture. 

 

Like I said - these are merely starting points - so a healthy dollop of sensibility is needed! I highly recommend buying the SU needle chart book available - part number ALT9601. Not only does it list all the needles and their profiles, nut a useful section in the front giving suggestions on how to select a different needle than the one you're using.