# Could someone please explain needle letters?

ekq, ekp, ejp, efp, emn, efn, ekn... What does all that crud stand for? thanks

Chris

Yea, and how do I relate those to how Yamaha has them lettered (NCVQ...OBDUT...)?

Lowedog

what you need boys is a link to the patrick burns web site that someone has a link to but not me any more. he must have changed his server or summit.

but it goes like this;

the first of the three letters is the angle of the taper. on a 'D' needle it's called .45 degrees (or 3/4 of 1 degree ok?) the 'E' needle is exactly 1 degree of taper so by the time you look at the points the 'D' is fat and the 'E' is pointed almost like a sewing needle.

the next letter is the middle letter and it represents how far down the needle when measuring from the first clip point it is to a measurement called 2.515mm. that is 'when the needle measures 2.515mm wide'. now because all the needles are wider than this on the straight bit; it can be and is half way down the tapered bit of a needle.

so if i had a DAP needle, 2.515mm would be very high up the needle. for DYP it would be right down the needle.

let's deal with the third suffix and come back to the second again. the third and last letter is the width of the needle before it is machined and is known as 'the straight'. so a DTL needle is thin and passes lots of fuel and is known therefore as a 'rich' needle and a DTP needle is wider, fatter and known as a 'lean' needle.

so how do they all tie in?

well, 2.515 width can be anywhere along the needle and the wider the needle is the longer it takes the taper when looking up the needle to reach the sides and vice-versa.

if we have a sharp taper moving in through 2.515mm to the middle we will have a sharper point but also the taper start will be lower down the needle so a ETM starts lower down the needle than a DTM and they cross at exactly 2.515mm wide and the ETM goes to a point and the DTM is still wide at the bottom, ok?

also if i change an EKM for an EKQ (the Q has wider straight) the taper reaches the straight higher up the Q needle than the thinner 'M' needle.

so when we measure a needle we never;

1) measure the width of the point or,

2) the taper start point

they both come about as a RESULT of our deliberations.

all figures come from where the needle is 2.515mm wide. THAT IS YOUR FULCRUM.

the next thing is to go back to this middle letter and get it sorted.

lets take two similar needles the EKN and the EMN. as said above the measurement to 2.515mm from the first clip position on the 'K' is 76.25mm and to the 'M' needle it is 77.15mm.

so these two needles have the same width, they have the same taper and they are identical bar when they are 2.515mm. well each clip groove is .9mm apart so if i raise the EMN one clip it's now identical to the EKN. so every second letter adds up to one clip position so as long as we are on about every second letter we can match them up; A, C, E, G or B, D, F, H etc etc.

the only difference between them is that there is .9mm of needle missing from the bottom of the EMN coz the needle is sitting one clip higher. this 1mm has no effect on the bikes running whatsoever. nil, zilch, ok?

we can take this further and have some fun with it.

EKN clip 4 is equal to EMN on clip 5.

they are both equal to EPN on clip 3 and ERN on clip 2.

also = to EHN on clip 6.

the only letters never used are i (eye) and o (owe). so as you can see what should have been EIN on clip 6 is EHN. do your alphabet here and it's easy, if not go back to school please.

we get our needles from two places. the first is a keihin dealer such as sudco or allins. keihin make their own needles made of brass and they are all coded OC so it's OCEMM whilst yamaha had some made as well and because these bikes are made to run on the road they are anodised and look like they're chromed; these are marked OB, so OB EKQ for example.

now there are huge gaps in the charts from keihin but yamaha seem to have made them just where they're needed. so between sudco and yamaha we can usually get what we want.

the official designation for keihin needles in the 35-41mm FCR carb is N427 so the code from sudco is now N427 OCEMM ok?

and that's it. so when as happened recently someone said that they had bought the EKN and the EMN just in case i'm sure you can now see the humour we get from this as it's the same needle but 1 clip apart!

always say what you do to the needle and never what you do to the clip.

"i lowered the needle". leave it to the other bloke to move the clip in his head, you've said the bit that matters and to explain anymore would be to 'bury yourself'.

if someone links us in to patrick burns site you'll have a visual as well.

Taffy

also:

Needle codes for 28-33mm (90xxx) and

35-41mm (OCxxx) FCRs are listed below.

Code Taper L1mm for

28-33mm

L1mm for

35-41mm

Diameter mm

A 56.25 72.20 2.605

B 56.70 72.65 2.615

C 57.15 73.10 2.625

D 0d 45" 57.60 73.55 2.635

E 1d 00" 58.05 74.00 2.645

F 1d 15" 58.50 74.45 2.655

G 1d 30" 58.95 74.90 2.665

H 1d 45" 59.40 75.35 2.675

J 2d 00" 59.85 75.80 2.685

K 2d 15" 60.30 76.25 2.695

L 2d 30" 60.76 76.70 2.705

M 2d 45" 61.20 77.15 2.715

N 3d 00" 61.65 77.60 2.725

P 62.10 78.05 2.735

Q 62.55 78.50 2.745

R 63.00 78.95 2.755

S 63.45 79.40 2.765

T 63.90 79.85 2.775

U 64.35 80.30 2.785

V 64.80 80.75 2.795

W 65.25 81.20 2.805

X 65.70 81.65 2.815

Y 66.15 82.10 2.825

Z 66.60 82.55 2.835

I learned more looking at the diagram Hick posted on this thread than I learned reading multiple threads about jetting. I guess I need to practice reading more often.

Holy crap that's complicated! thanks for explaining it!

Chris