Needle clip position or pilot?

19 replies to this topic
  • Guest_Guest_*

Posted January 29, 2001 - 01:24 PM


Just went to yz timing and put in ekp (evp?) needle#4, 48 pilot, 168 main jet. Power is there but I have to cross the void (wot dead space) before it kicks in. I'm thinking it must be clip position since I have good power on the bottom and strong on top. If I am correct, should I drop it to #3? Riding at about 4500 ft. Thanks for any info...don't want to pull the carb if I don't have to!

  • Clark_Mason

Posted January 29, 2001 - 06:44 PM



With the E series needles there is alot of interaction between the clip position and the MJ over 5/8 throttle--as compared to the D series needles with their more gradual taper. I would first try a 170MJ (easier to change) and then try the #3 clip. Run the same course to evaluate each change and try one at a time taking good notes.

good luck


  • Guest_Guest_*

Posted January 31, 2001 - 03:29 PM


Thanks Clark,
I followed your advise: the bigger main jet helped some (in fact it felt like more power on top), but the hesitation was still present. I ripped her out and raised the clip to #3. Results: worse than before! ( I also put back in the 168 main)
My new needle says EVP. I know that J.Dean said their parts fiche was wrong but why would they print it on the actual needle? Do I have the wrong one?
Any recommendations will help,

  • Hick

Posted January 31, 2001 - 05:01 PM


I believe the problem is you have the wrong needle. I made the same mistake and tried an EVP from Sudco. It made my bike run so horribly I’m surprised you are putting up with it. I didn’t get beyond my front yard before I put the stocker back in.

I’ll defer to James Dean if/when he sees this but an EVP is like 5 clip positions different (leaner) from the needle you need (EKP). That is why dropping it to #3 made it worse.

Here is the right Yamaha PN for the OBEKP (at least it worked for ME): 5JG-14916-EP-00

I have an ’00 YZF, ride at 4,500 ft. or so.

EKP #4
1.75 idle mix.

I know the WRs come with bigger mains, but I thought that was due to them working better with the D (DTM?) needle. When the YZ went to the E needle in ’00 (OBEKR) they dropped the main to 162 (I think it was like a 175 or something in ’98 to ’99. Whatever, point is that won’t the E needle like a smaller main? Or is the smaller main in ’00 due only to the displacement change (WR426 has a 165 right)?

  • Guest_Guest_*

Posted January 31, 2001 - 05:38 PM



  • Clark_Mason

Posted January 31, 2001 - 07:04 PM



The EVP starts its taper much later, is leaner longer and not a good match for this application--especially on transition to the main jet. The EVP is not going to work well and you want the EKP, EKN or EMN needle for use in this application.

James Dean or others can tell you where to get the needles and Part numbers.


[This message has been edited by Clark Mason (edited 01-31-2001).]

  • Michael

Posted January 31, 2001 - 07:44 PM


I've asked at several dealers for the EKN needle and nobody knows the part number. The part number that James listed for the EKN was 5JG-14916-EN but that number is identified as the EVN in the parts book (and by the dealers). See:

Does anyone know the correct part number for the EKN - or where to go look?

  • James_Dean

Posted January 31, 2001 - 09:41 PM


Anyone who gets an OBEVP needle should take their parts guy by the ear and drag him into the service department to have a look at the '00YZ426 service manual. The correct part number for an EKP needle is listed in the service manual 5JG-14916-EP. The parts fiche is WRONG.

Hick is right about the clip position. 5 clips leaner makes EVP#4 = EKP#?? off the top?

EKN is 5JG-14916-EN
EKP is 5JG-14916-EP
EKQ is 5JG-14916-E1
EKR is 5JG-14916-ER


[This message has been edited by James Dean (edited 02-01-2001).]

  • Guest_Guest_*

Posted February 01, 2001 - 07:02 AM


Thanks for the clarification James. I'll order the new needle but was hoping for a ride day after tomorrow. Can I run the stock WR needle with the yz timing? If so what jetting to accompany it?

  • James_Dean

Posted February 01, 2001 - 08:57 AM



Yes, you can run the stock needle with YZ timing. Start with the jetting that worked best before changing to YZ timing.


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  • Michael

Posted February 01, 2001 - 09:56 AM


James - Welcome back and hope you had a nice vacation. Thanks for the part number clarification! Every shop I went to checked the fiche and told me the 5JG-14916-EN was and EVN needle (I ordered one anyways so maybe it will get here someday). Do you have any sources that might have them in stock? Thanks for all the data (and the work you did to develop it) on the jetting. This gives us all a huge leg-up in the process. I'm glad that you are so willing to share!

  • Taffy

Posted February 10, 2001 - 02:33 AM



said it before, say it again

the more power you produce the more air you pump. the more air you pump the lower the jetting figures

i said it from the start & i've used it to mark everyone's card.

yes i know it's unfair to watch others struggle with the figures but sometimes it's good fun!

check those main jet figures & even the pilot jet #'s again & note the one's for the '00 & '01 YZ also the '01 WR. what do all three models have in common?



[This message has been edited by Taffy (edited 02-10-2001).]

  • James_Dean

Posted February 10, 2001 - 11:54 AM


#162 main and #42 pilot


How many YZ400's do you see using a #162 main jet for more power. More like a #175+ with the DVR needle.

Bottom line here is the EKP and EKR needles pass up to 30% more fuel at WOT and need a smaller main.

You are comparing corked up WR jetting that sells in California to closed course YZ jetting with EK- jetting.

The #42 pilot goes with the newer FCR2 carb.

  • Andrew_in_OZ

Posted February 10, 2001 - 12:06 PM


Confuse us some more,If what your saying is corect then why when you open up the exhaust & de-restrict air box to improve airflow & power do we use a larger main and not a smaller one?


  • Taffy

Posted February 10, 2001 - 01:19 PM



when you de restrict an engine as opposed to tune it the jetting goes up. only when you tune it does it come down.

the waves are reduced at the inlet so the airspeed doesn't go like heck then stop then go like heck again picking up lots of fuel by to it's high airspeed.

instead the air finds it easier to get in so the pulses are lost, air slows down but doesn't stop start like before.

with no strong airspeed there is no drop in atmospheric pressure at the emulsion tube. to get the right amount of fuel in you then have to jet up as a compromise.

the same goes with the exhaust. no blockage means less powerful pulses. airspeed is slightly slower but continues non stop. the exhaust alone doesn't have such a big effect.

when you tune-with one or two exceptions like porting the head right out- the engines volumetric efficiency goes up & the powerful pulses return & for longer. so the jetting goes down & down.

have you heard of the masonic lodge over there? the above is one of the diddly-diddly handshakes of the tuners.

go into a tuners store & say i put a bigger jet in & it went like snot! & he'll say he has nothing in.

say that the jetting keeps going down & he'll welcome you through to the auditorium.

as for the PJ's i'm still right JD.
as for the MJ's you haven't answered MY question yet...

anyway, a 426 should run a smaller main by one, than a 400. given the closeness of the capacities though this probably isn't valid. but it is on other machines when you compare like for like.

tried your EKP today & felt a difference at mid throttle. i have the MJ to sort. also slight stutter at off idle. i'm doing a trailcross tomorrow with it as it is & will experiment with it soon.

shall we continue with the PAJ here?

i'm going to try & use the extra suction of my machined slide cutaway with the leanness off idle.


  • James_Dean

Posted February 10, 2001 - 08:21 PM



Hick's numbers on pilot jet size were incorrect. The '00WR400 also has a #42 pilot jet stock as do the " '00 & '01 YZ also the '01 WR".

What do the 4 bikes have in common? Not displacement, but the FCR2 carb. Which by the way has a pilot jet that does not interchange with the FCR on the other 400's. The slide is different too.

It will be hard to draw detailed conclusions at this rate.

I would like to try a larger pilot air though... :)

The main jet on the 426's (#162)certainly does look smaller than what most 400 owners are using(#165-#170+) with the EKP. Looks like you may have a point well taken here. My local temp is at 40-60F mostly, so it's not a general standard for most. Think a few more YZ400 owners might like to sort it out for us? :D


[This message has been edited by James Dean (edited 02-10-2001).]

  • Taffy

Posted February 11, 2001 - 02:15 PM


it's not what the 95% decide, it's what the 5% who know what they're doing decide.

i might be half welsh but i'm no sheep!


[This message has been edited by Taffy (edited 02-11-2001).]

  • Hick

Posted February 12, 2001 - 10:41 PM


Originally posted by James Dean:
Hick's numbers on pilot jet size were incorrect. The '00WR400 also has a #42 pilot jet stock as do the '00 & '01 YZ also the '01 WR".

I didn’t mention pilot jet sizes in my post other than my own, but I did think the ’00 WR had a 45 pilot (are you reading my mind?), this is listed as “STD” on Ronnie’s Fiche.


I understand completely what you are saying, I’ve jetted various bikes and have noted the difference in main size especially between 500s, 250s and 125 two strokes and also between large and small automotive engines using the same carb.

My post was only an effort to reconcile the theory with Yamaha’s practice. The YZ 400 has a larger main than the WR 400 yet they are the same displacement. The WR 426 has a larger main than my YZ yet they are the same displacement.

I think you should give Yamaha a call and enlighten them, it appears they could use it. :)

  • Taffy

Posted February 12, 2001 - 12:14 PM



we know that a yz needs a richer MJ if only for the open v closed exhaust.

the other way round though with the wr426? mmmmmmm!

there's a reason for everything. just gotta think it through. to be honest, one jet size ain't a lot either way is it.

i can't help but look at that dyno chart in technical. the graph has a huge hole at the low end. gradually it's being eroded.

i re read an article on the vortex ignition posted by mitch & porritt, a bit whiffy. reads like a soap advert!

in your article 'raise the needle' you said APJ twice when i think you meant PAJ, just check it.


[This message has been edited by Taffy (edited 02-12-2001).]

  • Hick

Posted February 12, 2001 - 01:35 PM


Originally posted by Taffy:

we know that a yz needs a richer MJ if only for the open v closed exhaust.

Oops, I forgot completely about that. I’ve only seen a few WRs in person, they both had aftermarket exhausts. DOH!


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