Meaning of letters on Needle?


10 replies to this topic
  • sandrappy

Posted March 15, 2013 - 02:19 PM

#1

Tunning my 2006 yz450f after some mods. Anyway at idle and wot i'm spot on with jets. However right as soon as i give any amount of throttle till about 3/4 throttle i'm lean. Super lean right off idle and slowly gets better through the rpms.

My needle is stamped NFPR, so i need a samller diameter needle, which i think should richen it up all the way through and put me where i want. What needle would i need to order from yamaha?

Typically I'm familiar jetting aftermarket carbs and they have a break down of the different numbers and how they affect the size of the needle, taper, length etc.. But yamaha doesn't have a chart like this. Called a yamaha dealer and they simply said the last number is how rich or lean, but don't say where it is rich or lean... And there are needles with different leters in both the last digits.

anyone have any idea on what i need or what the letters mean on the OEM needles?

  • Krannie McKranface

Posted March 15, 2013 - 06:52 PM

#2

Just use the NCVS needle and you will be fine. That is the Go-to needle for the FCR carb on Asian off-road bikes.
You need to pair it with 45-48 pilot, 160-170 main, 50 leak, stock air jet, stock power jet ( or one large for very cold climates), and a slide that is surely set to the bottom of the rpm range before adjusting the fuel screw.

How do you know you are lean in those throttle sections? You can't feel lean.

http://www.google.co...Q9QEwAA&dur=357

  • GuyGraham

Posted March 16, 2013 - 05:49 AM

#3

needle codes & what they mean are all in the work shop maual - Yamaha use the same codes as off the shelf FCR needles
download it from the Australian Yamaha website

  • sandrappy

Posted March 18, 2013 - 02:35 PM

#4

Krannie, thank you for the link but that does not show the OEM numbering of their needles. All yamaha needles start with a N then 3 extra numbers. That chart is showing a different lettering scheme. I know it is lean because my wideband o2 sensor is reading lean. Thus i want to know which letters correspond to the diameter of the needle to order a slimmer needle to richen up throughout.

GuyGraham, By the work shop manual do you mean the service manual? i already have it and flipped through quickly but did not see where it listed the different needles.

  • sandrappy

Posted March 18, 2013 - 02:44 PM

#5

Krannie, thank you for the link but that does not show the OEM numbering of their needles. All yamaha needles start with a N then 3 extra letters. That chart is showing a different numbering scheme. I know it is lean because my wideband o2 sensor is reading lean. Thus i want to know which letters correspond to the diameter of the needle to order a slimmer needle to richen up throughout.

GuyGraham, By the work shop manual do you mean the service manual? i already have it and flipped through quickly but did not see where it listed the different needles.

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  • GuyGraham

Posted March 19, 2013 - 11:28 AM

#6

From the YZF Manual
Start off with the std NFLR needle and go from their

You have the NFPR needle which is slightly leaner than the std needle on the parallel dia which is 1/8 to 1/4 throttle
If you want to richen up, up to 3/4 throttle either lift the needle up 1 or 2 clip positions or go for a needle with the greater taper, which would be NGPR
Posted Image

Posted Image




As we're in the WR forum, from the WR manual

In the WR, use the (G) DDUQ needle which is supplied by yamaha with the bike (but not fitted due to emissions crap), with the needle in the 3rd groove from the top
Posted Image


Finally, a general purpose table on how to decode the FCR needle code

Posted Image

Edited by GuyGraham, March 19, 2013 - 11:48 AM.


  • sandrappy

Posted March 21, 2013 - 02:14 PM

#7

Thank you for the manuall pages.

The second diagram you posted is the sudco diagram. I have called them and there needles are completely different then oem, and you can't cross reference them. I've always used sudco in the past but the sizes and tapers on their needles has nothing to do with the OEM ones.

  • sandrappy

Posted March 21, 2013 - 02:32 PM

#8

Also just to make sure i am reading it righ. Currently I have the needle lifted all the way up and from 1/8 throttle till about 3/4 throttle is lean, very lean. Even ran spacers under the needle and it was still lean.

Anyway I want to try the richest needle they have, based on that chart i should order the NFLN needle.

My bike was leanest right as soon as i crack the throttle and then slowly gets better, but even cruising at part throttle it is still way to lean.

  • GuyGraham

Posted March 22, 2013 - 07:41 AM

#9

Thank you for the manuall pages.

The second diagram you posted is the sudco diagram. I have called them and there needles are completely different then oem, and you can't cross reference them. I've always used sudco in the past but the sizes and tapers on their needles has nothing to do with the OEM ones.


Are you sure - Yamaha just buy the carb (and alternative jets/needles) in from Kehin - they don't make their own
My DUQ needle measures 2.74mm on the plain section, bang on what it should according to the second diagram



Also just to make sure i am reading it righ. Currently I have the needle lifted all the way up and from 1/8 throttle till about 3/4 throttle is lean, very lean. Even ran spacers under the needle and it was still lean.

Anyway I want to try the richest needle they have, based on that chart i should order the NFLN needle.

My bike was leanest right as soon as i crack the throttle and then slowly gets better, but even cruising at part throttle it is still way to lean.


Something not right here

Are you sure you AP is working correctly - crucial for avoid bogging when twisting the throttle. You can't compensate for a non-working/badly adjusted AP squirt by going richer on the needle
Does your squirt hit the slide?
what is the duration of your squirt?
Have you done the O-Ring mod?
Have you tried going down on the leak jet?

Edited by GuyGraham, March 23, 2013 - 01:25 AM.


  • Krannie McKranface

Posted March 22, 2013 - 09:24 AM

#10

Are you sure - Yamaha just buy the carb (and alternative jets/needles) in from Kehin - they don't make their own
My DUQ needle measures 2.74mm on the plain section, bang on what it should according to the second diagram


Are you sure you AP is working correctly - crucial for avoid bogging when twisting the throttle. You can't compensate for a non-working/badly adjusted AP squirt by going richer on the needle
Does your squirt hit the slide?
what is the duration of your squirt?
Have you done the O-Ring mod?
Have you tried going down on the leak jet?


DITTO

  • Thommo_400f

Posted March 22, 2013 - 01:39 PM

#11

Don't disregard the influence of the main jet on your needle.
If I run a 160 main I have to run my needle on #1 but with a 155 main I can run same needle on #2-#3 and get better low - mid response.
You have to get your pilot circuit set properly first because all of the systems contribute a volume of fuel to the system to add up.




 
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