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Yamaha part No 5TA-14916-vs

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Hello Folks

 

Here are just the facts.

 

Yamaha WR426F 2002

 

I am about half way through the jetting experience,this is whats been changed.This is my set-up.

 

PJ# 45

MJ# 165

FMS 1 1/2 turns out

AP spring,& cover

Airbox lid modified 3x3

Needle OBDQR 4th clip position

No leak jet fitted to this FCR-MX 39 carb

Standard header,DEP slip on  performance exhaust

Clean air filter

No bog,very strong performance,1/2 throttle/off the gass flutter?strange maybe a lean spot?

 

The bike has 21inch  & 18inch wheels fitted with pirelli scorpion MT90 mixed tyres.i ride 95% on tarmac roads/streets,fast urban commuting,that kind of thing.I changed to 14t-48t sprockets to give me driveability and top speed.I live on a sunny island,around 20-25 degrees all year,i working at sea level,and live at 750 meters,never rains.

 

At this point in the jetting experience i know i have cut some corners,and need to play catch up if im gonna benefit fully.

 

I have not yet:

replaced slide plate seal

replaced AP diaphram for a new one

replaced main nozzle

or checked the size of the starter air jet

or lifted up the subframe and set the timming of when the AP starts 

I will do this.

 

 

 

With the settings above i achived very strong performance,no bog!     the 1/4 thottle very strong, 1/2 throttle very strong,3/4 throttle very strong, now it will rev out no problem,very fast top speed.

If i roll on the throttle,it pulls very strong.Like a train!

If i WHACK !!! the throttle open fast,it just points for the sky,really very instante,and powerfull.

The overall burn is a little bit rich and sooty on the spark plug,but also i can see a coffee/white lean spot right on the electrode.

Performance is outrageous!!

 

 

Here is where i need help please.

But right in the middle of 1/2 throttle between engine braking "off the gass"and "on-the gass" is this strong flutter,it kind of sounds like it pops and cracks( lean ).But when you get on the throttle,it just clears and 110% brutal power,no delay,no bog,very very strong........but not right!! this was with the original OBDQR needle.

 

 

I have the same settings,but have changed for a #NCVS needle.Could not find one in Europe,so shipped one from Japan Parts depot,5TA-14916-VS #NCVS.

 

 

The lean 1/2 throttle,kind of off- the gass flutter has gone,much better,the 1/4 and 1/2 throttle response is now very very smooth and fast.

But the bog has now returned at around 3/4,sometimes when you want to roll on the throttle,you have to wait for the revs to rise and the engine pick-up.less power?

 

 

It was not like that with the OBDQR needle 4th clip.

 

Where do i go with this #NCVS needle? do i try another clip position? maybe 3rd?

 

Thank you.Hope you understand my description.

 

 

Thanks for the forum and all the info i have learned from everybodys input.

 

 

PS.thanks Kah Ran Nee for all your great posts and answers.

 

 

 

 

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I am very happy with the bike,its a 2002 model,only problem was to change the 3rd - 5th gears and selector forks,to correct slipping dog gears.Its a classic.

 

I was so crazy about trying out the #NCVS needle,and yes in parts the first 1/2 throttle openning is silky smooth n fast.

 

But its realy affected my 1/2 throttle roll-on response and brought the Bog! back.

 

Who needs that,im looking for performance somewhere between the two needles.

 

Thanks.

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I'm not experienced with the OBDQR needle, but I just read that nthe OBELN needle works great in the 426

The NCVS not so much.

 

By the description of it's properties, it sounds like it might work out well in my Wr450 with a stage 3 ported head and YZ cams....

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Thanks Kah Ran Nee

 

The OB DQR needle is listed in the owners manual as standard/on the scale of lean to rich it sits at the half way point : lean DQU-DQT-DQS-DQR-DQQ-DQP-DQN Rich

 

So from what your saying the #NCVS just might not be suitable for the WR426F 2002.

 

Ok ,maybe i might try a DQQ ?? slightly richer,and maybe smooth out the 1/2 throttle flutter and give me back my 1/2-3/4 roll on,bog free.

 

The #NCVS was a pain in the ass to find,so i might experiment with another clip setting,go down one? number 5,give me some more gass,open up the top end again?

 

I have just fitted the needle(#ncvs).. today,and will now try the bike over several days under nornal use, to draw a conclusion.

 

 

 

Thanks

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Hello Kah Ran Nee

 

Sorry totaly miss-read your post!

 

You said the OBELN needle works great on the 425,ok well,we might be on to something here,im gonna track one down.

 

 

 

Thank you

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OK i just found these:

 

OC DVR

OC DVT

OC ELQ

OC EMN

OC EMP

OC EMT

OC EKR

OC EVR

OC FML

OC FMP

 

i dont see the OB ELN,i think this is a yamaha part number and i looking at the Keihin parts!!

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Yes your right,its now widly available,only i live on a small Spanish island,UK Yamaha had none in stock,and had to order from Japan parts depot.I found the yamaha part number on thumpertalk.

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Hello Kah Ran Nee

 

Where were you able to read about the properties of these needles?

 

 

You recommend OBELN needle ?  how can i find out more about its properties?

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i found the detail,from a post way back in 2002,talking about best performance of the426 with standard tail pipe.

 

Maybe the OBELN might work for me.

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I have never found a needle chart that show OEM part numbers, so you will have to do some digging to convert them to Keihen, or find their place in the range.

The OEM needles are usually just that; for OEM applications only, so they are not on the Keihin charts

 

http://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-OC_FCR_35-41mm.html

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did you read the jetting stickey in the Yamaha wr426/450 section and why have you not simply put a yz carb from 2006/2009 ? things get easy from their on if you did not know.

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Thanks peaceofwork

 

I did not know about the 2006/2009 YZ carb mod.

 

Im gonna check back,and find out more.

 

Cheers.

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OK i think all the WR & YZ carbs are all the same Keihin FCR-MX .Small differences on the newer carbs,and jetted for intended application.

 

Im gonna carry on with the fine tunning on my 39mm FCR-MX 2002,its the original carb for the bike,and works well.

 

Strange the #NCVS needle works so well in the 450,but just is really a little bit off when used on the 426.

 

I checked through the 400/426/450 jetting sticky and for the 426 EMN EKP DRR seam to be a popular needle. 

 

I also gonna re-check the technical link ,for needle size/letters that Kah Ran Nee posted,thank you sir.

 

 

Thats all for now.

 

Thanks

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Hello Kah ran nee

Thanks for your reply/update.

I have been looking at all the needle charts,Keihin and Yamaha.

And so far have grouped the needles into familys,from my Yamaha owners manual they use " N P Q R S T U " system,"N" being the richest and "u" the leanest.

I think i can see a pattern here: DRN,DQN,DUN,DVN,DJN,FMN,EMN,EKN,EJN,EUN each family running from " N to U ".

I need to spend more time on this and maybe produce a spread sheet type guide,starting with the needles i have used and a description,not too dificult if everybody helps.

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But in getting stuck when i see part numbers like: NCVS,NDJP,NEPO,NFPR.I guess these are needles produced by Japanese manufactures??

I have been through the jetting database YZ 426/450 and also WR 426/450.

And need some input with an update on the jetting database,because it not very well supported.Often the needle section is listed as STOCK,well if we know whats stock is(part number please) and how well it works for you, we can fill in some of the blanks,maybe produce a chart,or even a smart phone app ?

Also many,many people use a JD blue or red needle and this is no help when trying to select the RIGHT needle.

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I am still using the 5TA-14916-VS #NCVS,on my WR426F.

I did lift the subframe and check AP squirt.

It looked late starting ,after the flat slide lifts.

I made an adjustment on the AP timming screw,to try and get the squirt to nearly hit the slide as it opens.CCW?

After trying the bike fully warmed up,it was worse,bogged badly,and ended up re-adjusted the timming screw back to its original position,as this gave me best response??

Now im gonna try clip position,as i went stright for No 4, i want to try clip position 5 and 3.

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