YZ timing,pros and cons

I am considering going to YZ timing,My dealer says that you should not do it because the cdi box is not programmed for it? and in general does no recommend it..My question is, has any one experienced any ill effects? Are there any jetting changes if you advance timing? Thanks for your help...



i am putting mine back to the WR timming so i do not have the problem with dieing just off idle when i go to take off. today is the first itme i rode with YZ timming and found the bottom end all gone. it was at the top end. i do not need the top end for the type of riding i do. the single track techincal riding is toooooo slooooow for YZ timming.



yz timed now

some mods


at least try to get the jetting sorted!

tell us what jetting you're running and we'll have a go. describe what the bike does more accurately if you can. is it standard?

your symptoms are those of too lean a needle straight. _ _P? or _ _ Q?

your bike should go like hell from the off.


ok here it is as best as i can remember(it is all written down i a log i miss placed)




emp#2 clip

yz timmed now

air box lid gone

zy stop screw

tps min.res(to get max timing)

gray wire out of plug and insulated

plug out of exhaust

the problem is i drove 5'(go to take off) and the bike would cough out of the carb and die i would fall over. then i was on an up hill and going slow on marble rocks i wanted more speed twist the throttle and the bike would jump then i would fall. so i was picking it up all day. this did not happen before YZ timming. i have a EKQ needle on order. the jetting is so close now i think this will complete it.

let me know your thoughts.



yz timed now

some mods

THe YZ timing is by far the best mod you can do to this machine, other come in very very close to the performance gain but the timing is a HUGE improvement. Like Taffy says however you need to have the jetting correct...please dont discourage other people unless you have worked out ALL the bugs (jetting) and have given it a good go. I feel once you have dialed in the jetting on your YZ timed bike you will be blown AWAY, i just put a YZ pipe on my bike and taffy advised me to put the main jet up to a 178, all I had in my kit was a 175 so I threw it in to check it out and it made a WORLD of difference......go ahead and tinker...I have found the smallest tweaks make HUGE improvements sometimes!


01' WR426,YZ timing,EMP #2,#48Pilot,#100PAJ,#175 Main,BK mod,Kouba T-Handle,YZ pipe-no baffle, open airbox,Gray-Wire Pulled,K&N Filter, throttle stop mod,CA Street Legal,Pure SuperMotard 17 in. wheels, 15/46 gears,ProTaper bars,

Also Slashman you off idle problem may be easily solved with the BK mod, this is another "MUST DO" modification to these machines, there is WAYYYYYY too much fuel on the initial squirt going into the engine...this is almost certainly your problem.


01' WR426,YZ timing,EMP #2,#48Pilot,#100PAJ,#175 Main,BK mod,Kouba T-Handle,YZ pipe-no baffle, open airbox,Gray-Wire Pulled,K&N Filter, throttle stop mod,CA Street Legal,Pure SuperMotard 17 in. wheels, 15/46 gears,ProTaper bars,

Hey Slashman,

Sorry I didn't make it out Saturday, I ended up going to Speedworld and got talked into racing in my first moto.

Well, don't get me wrong here, but is there chance you didn't do something right when you made the timing change? I did my 250 this past weekend and woa what difference.

Just asking, might be worth checking before you give up.



2001 WR250F

White Brothers E Series Full exhaust

Panoram computer

Tap Bars

jet kit

YZ timing

Grey wire mod

Pro Rally hand guards

YZ plastic

no i am not giving up yet. this was my first imperssion. will have to put the other needle in and see what happens. i am puting a EKQ. this will be the leanest needle yet.(except for the stock one i took out).i am going to recheck it even though after the mod the bike started with the normal 2 kicks when cold. also a small part of the problem i did not have the suspension soft enough.(getting bounced all over the place)

i do have a few questions about the BK mod.

would you want the biggest squirt you can get to keep the instant respnose?

does any one know how many cc's the squirt is in the factory set up?

would it be better to have leaner jetting and let the acc. pump do it's job? you could get better gas milage if that is a concern.


good thing you did not go on saturday. saturday's ride was a disaster also. long story i will tell you later.



yz timed now

some mods


Keep in mind, the accel pump provides enough gas for 4 carbs. This carb was originally used on superbikes where only 1 of the 4 accel pumps was hooked up and it fed all the carbs. Sucdo told me this and this is what convinced me to do the mod.


you appear to be a little weak on the MJ. you have the same jetting as my euro pipe and less than the YZ pipe (165 and 175) your opened yankie pipe would be a 172 /175 i think.

you have an imbalance of PAJ (#80) and PJ (#45) so which do you move? i would bring the PJ down to 42 and play with the PS.

PJ45 = PAJ #100

PJ42 = PAJ #90

PJ40 = PAJ #80/75

just ride around at 5mph trying to pop throttle wheelies and adjust the PS by jumping on and off. no gloves, you know etc etc.

those wheelies aren't in 5th ya hear!

you have a _ _P needle which is as lean as you want. the _ _Q will kill you! you're stalling because the needle is "too fat" which equals lean.

then you get the same amount of fuel as me off the pilot system AND YOU GET THE ACCELERATOR PUMP on top. this will basically hit the plug as a solid globule and literally wash out your spark.

so get the BK mod done. better still be the first person after me to disconnect the APJ completely and watch it really fly!

to conclude;

MJ up to 170/175

PJ down to 42 or even a 40

disconnect the APJ or at least do the BK mod.

muck with the PS with 5mph snap wheelies

needle should be a _ _M, N or P (prefer M n' N)

good luck


[This message has been edited by Taffy (edited October 09, 2001).]

yes i am going back down on the pilot to a #42. and i learned somthing else if you run your needle in clip#1or#2 you do not get the full main jet circut. the carb was designed to run in clip#4 so #3 is not so bad but #1 does not let the needle come up far enough. this is the reason for the EKQ. to see if i can get back to at least clip#3 if not #4. i hope this works.



yz timed now

some mods


are you at sea level?

std MAJ at #200 yes?

don't worry about the clips 1/2 and 6/7. your changes are of a PROFOUND MAGNITUDE and no i can't say that again! that's the kind of thing graziano rossi worries about but not you and i.

if you wanted your needle to operate in the middle clips your EMP should have become an EPP (clip 3) or an ERP (clip 4) but you've changed the straight as well which you may not have wanted to do.

the needle straight does your tickover, it dictates how much choke, it affects the first ONE yard-no more-as you move off.

the rest is pilot system/APJ.

below for everyone's sake i describe two needle straights on my bike. sea level (30ft below as i live in the fens which are shrinking at 1' every 10 years)

a _ _P needle

from cold it takes a lot of kicks, it won't rev for a few moments and then it goes nuts and i have to run over and push the choke in. this often leads to a blipped throttle to keep it going and it dies.

if you open the throttle too quick it hesitates, tickover is up half a turn on the idle knob.

a _ _M needle.

starts first time and the revs are immediately slightly higher but steadier, you think "crickey if the revs rise by the same amount it'll explode!". but they don't, it stays the same all the time.

you know you have a richer needle in so you think that after a minute it will start to eight-stroke; but it doesn't. idle screw down 1/2 turn (this is an improvement not a fault).

when you go to move off the first yard isn't a problem. anon.

instead of the needle you ordered you should look at the EMN or EMM like me and if you're looking ahead then i think the EPM/EPN or ERM/ERN would have been right.

in all the things i've written today the thing that ruins your (plural) results is the APJ.

i hope your dealer will swop your needle. good luck.



I am from the 250F side and maybe you can help me a little. My bike runs great except I think it can run better in the mid (it appears to be too fat in the mid) It doesn't have a crisp response. At a race a few weeks ago I rode a friends 250F and it was crisp so I went back and moved the clip up to the 2nd pos. from 3rd pos. and got that crisp feeling. I am currently running in the 3rd pos. I know if I moved it to the 2nd position it would be about right, but I always thought you wanted to try and keep the clip pos. in the middle or change needles. Right now I am running OBELP 3rd little to rich not much though. Was going to try OBEKP needle. I'll try this needle & also moving clip in 2nd pos. on OBELP. what are your thoughts? Did I confuse you.

bike destroyer

i can only speak generally, i'll give you my feelings and if they don't add up in your mind then don't do them, ok?

first, when you move a needle you richen the mixture at 1/2 throttle which to you and me is 4th gear. trouble is it moves the taper start point as well. for us thought this isn't ultra critical.

i would have no hesitation in going down to clip 1 to see what happened-or up to clip 7 either. infact i've done several tests with a spacer under my needle representing clip 8. i had to stop there because only 1mm of needle was pushing against the ET at WOT!

are you sure you have the correct MJ? with this carb the MJ heavily changes the mixture where the needle works.

last week i had my needle just about spot on, put in a larger MJ and it helped mid revs right where i would expect the needle to work.

so get that MJ right. then drop the needle one clip. if that doesn't work put a .5mm washer under the clip! so your halfway back up.

ELP on clip 2 needs to be EQP to get to clip 4 again.


[This message has been edited by Taffy (edited October 09, 2001).]


i have the main air jet is std. and at ~800'. i have plenty of needles to choose from. i am going to try the EKQ this weekend at a higher alt.



yz timed now

some mods


Thanks for your thoughts. I am pretty sure my MJ is correct. If I change that in either direction it is either way too fat or too lean. These 250F seem to be very responsive to small changes on carb settings. I'll just play with the needle settings & maybe some different needles. Slashman has a bunch of needles he said he would let me try (that's where I got the EKP) Thanks Slashman.

I bought a '99 WR that the dealer had

YZ timed for the previous owner. It

too stalled off idle all the time. I

opened it up to put it back to WR timing

and saw that the dealer had rotated

the exhaust cam the wrong way. It

wasn't WR or YZ timed, it was just screwed


does anybody live close to co.jim ?? that has the yz timing on the wr? i live in colo spgs my bro has a 00wr400 w/yz timing we ride 717(woodland park ) all the time and he loves it !!!!


Me and Slashman and maybe some others will be going on a good ride next weekend. Oct. 20/21. It will be a good ride I hope to see you on this one.

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