James,Taffy,Clark etc...

G'day everyone,

How are all your bikes going with the MODS done a couple of months back? Has anyone made any other modifications or changes? My bike is running extremely well at the moment with the following settings:

Modified FMP#6

#162 MJ

#230 MAJ

#48 PJ

PAJ(S) 1 1/2 turns out

PS 1 1/4 - 1 1/2 turns out

AP 1.2 mm stroke

In race curve on the vortex cdi the bike is WAY FAST ! It's unreal.

anyway let us know how your all doing.



"00"WR400,YZ timing, Modified FMP needle,

Modified Acc pump&MAJ.

VORTEX dualcurve ignition

11,800 RPM red line

Staintune s/s exhaust & header...

Somebody stop me !!!


I am running the EKN needle (#4 position)with the air passage drilled out. I am extremely happy with the hole set up. The bike runs extremely well. The E needle was certainly an improvement. I haven't made any significant changes from the set up you and JD recommended. You guys have made it too easy for me, I feel like I have cheated because I get to skip all of the R&D time.

48 pilot, 100 pilot air, 172 main (pretty sure, wrote it down in manual), 2.78 air passage, 2.26 (#43 drill) MAJ, 3/4 turn out, DSP tapered pipe and exhaust.

One thing I noticed is that the bike warm starts very easy without the hot start button needed. But it doesn't seem to be too lean because the choke is only needed for about 10 seconds.

first of all you ozzy twit where the F*** have you been!

you treat me like this once more & i'll come down there & scratch your eyes out. bitch!!

better still i'm sending a rugby team down that's going to make you feel like you're having your teeth extracted so i shall console myself with this smug thought.

i've had a right old time setting mine up. first of all i'm too busy.

i put the MAJ in that i had drilled to 2.3mm & it immediately was a 7/8 throttle improvement. i probably won't even bother experimenting with this for a while.

i fitted my powerbomb header & felt an immediate improvement. small but none the less an improvement.

then my problems really started, i fitted the stroker tailpipe but i didn't get a nice fit because the tailpipe has a huge bore size. the bike wouldn't start no matter how much i kicked. when it did run it stalled.

anyway i did run it & as i've noticed before when you run these things lean & get all the backfiring, popping & banging the plug gives out the next time you go to start it.

i went to a 52PJ & tried lots of settings, till in the end i said "**** it!" & left it for three weeks.

i'm back to the PB header & the standard tailpipe. the jetting has gone back down to a 45 PJ. the needle is a EFM on clip No5.

i'm going to get this needle & the header just right before i try that tailpipe again. when i do swap, i'll try to do everything while the bike is hot. i think that the header pipe affected the jetting without the bike making it obvious in my one-day's riding.

i've gone from a 168 MJ as was, to a 180 with the tailpipe & now i'm back at a 162 & i'm due to go down again.

i'm trying to lift & lift the needle again whilst modyfying the closed to 3/8 throttle towards leaner on the pilot jet.

we'll see.



What's the best way to set the AP to 1.2mm? Also, I'm not sure if 1.2 is a good "baseline" to start at or is this more of a "custom" setting just for your bike. I'll give you my settings and let me know what you think.

EKN #5 Needle

168 MJ

48 PJ

200 MAJ

PAJ Screw 1 1/2 out

PS 1 1/4 out

YZ Timing

Vortex Ignition

Stock Exhaust

Thanks, Jason


Haven't changed anything in some time. Close to the shop the jetting has been-

#170 MJ

#230 MAJ


#48 PJ

PAJ 1 1/2 turns out

PS 1 1/4

AP 1.5mm

YZ exhaust

This hits hard and is fun to play. A little rich in the upper mid-range.

This summer I will go back to EKN#3-#4 w/#172 main for the longer 70-100 mile rides using the spark arrestor screen in the YZ muffler.

The same E taper needles are working in the orange and yellow thumpers too. It's becoming a trend. :)


[This message has been edited by James Dean (edited 05-18-2001).]

I had my double hernia surgery and an just now starting to ride but only on the road. Been really concentrating on breaking in my HRC kitted XR650R-what a power high riding it is but if I tip it over its a tough pick up just yet.

Will start riding the Yam soon as the high country trails will open soon and thats where the WZ420 shines. The WZ is currently setup as follows

PJ = 48

fuel screw = 1.25

Needle = EKN clip #4 from top

Main Air Jet drilled out to 2.26mm

Pilot Air Jet drilled out to 1.32mm

Main Jet set to 172

Accel pump stroke 1.5mm

I gleaned this jetting combo from the work of the forum (Taffy, James, Andrew, etc.) and some of my meger understanding. We will see how she goes.

Exhaust PowerBomb (a excellent header) and the old style Stroker SX-1, not as strong as some others but quieter.



John glad to hear everything is working well,keep them grreenies out mate :)

Taffy you've got to started buying lottery tickets or something, your luck must turn around soon. :D

Jason there are various ways of reducing the AP depending on the model of your bike/carb, do a search on acc pump there are some great threads on this topic. 1.5mm stroke would be a good "baseline" start for your set up.

James have you tried the needles you were modifying,the modified "F" I'm using has so far been faultless in all terains and conditions. I think the "E" is more then a trend it's contageous!

Clark great to hear youre getting back on two-wheels, the 650 would be fun to ride there are some open fire trails not far from here where the big bikes realy shine.It will be interesting to see how the modifications work with the extra capacity & compression of your bike.

Hope you all have a great weekend,



I have not tested the modified triple taper EMN/EMP needles yet. As time permits they will get compared. It will be close to what I'm running now, so don't expect a radical difference.

How did you arrive at the #162 main? Looks smaller than previous "best" choices.


a lot of the MJ comes down to how restrictive the tailpipes are.




All previous testing was done using the WR/Traction curve on the Vortex CDI and EKN needle and at the time most leasure riding was done in tight, steep, rocky terain so was verry rarely at high speed (except for during testing). Lately Ive been riding some high speed open trails where the YZ/Race curve and "FMP" have been a LOT of FUN but was running a little rich from 3/4 - WOT so I went down to a #165 then a #162 which cleaned it up, In WR/Traction curve It feels like it might be a touch crispier but does not have a lean hesitation at all so it may have made a slight improvement here also.


The Staintune is an AUSSIE Made stainless system similar to the YZ set up it gives me an extra 3-5 HP over the stock system.

PS Can't wait for that rugby team of yours to get here :) results will be very interesting!


[This message has been edited by Andrew in OZ (edited 05-21-2001).]

I ran my WZ420 with the above jetting and it was too rich on top and too lean on throttle closing even with the fuel screw at 2.5 turns out. Took another PAJ and drilled it out to 1.04mm vs the 1.32mm to slighly richen up the bottom and will go with a 168 or 170 main jet.

The next test on this bike which has served the fourm well as a test bed for an assortment of parts mods etc. will be conducted by its new owner as I sold the WZ 420 and got down to one bike for a while--my HRC kitted and as usual fairly tricked out XR650R a very fast ride but not as good in the tight stuff but a great dual sport ride. A friend of mine who lives close by purchased the WZ420 and I will be riding with him often.

I will continue to monitor this group to see how the story continues to unfold.

James Dean please send me a e-mail as I had to completely rebuild my computer system and lost all my stuff and would like to keep in contact on jetting issues and solutions.




thanks for sharing your findings, I imagined there would be a slight difference with your engine mods.sorry to hear about the sale of what sounds like an incredible bike and I hope the 650 brings you plenty of fun and enjoyment.

All the best,



Thanks also for the great support to all of us WR owners. You have really helped us learn a lot and shared your many hours of testing to make it easier for everyone. You have an incredible number of postings, 676 since joining Feb. 2000, and every post has always been something worth reading.

Keep us informed on your latest project and keep checking in when you can.


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