Jetting & Suspension results !!!

I need to start with my suspenson.....This is by far the best mod I have done. I was on the bike for the first time over the weekend and it felt great. NO more bottoming and was awesome in the woods. Thanks to MX TUNER.

Good job mark :):D jetting, I have some work to do.

YZ Timing & Deoctopused

EKN clip-4

168 MJ

48 PJ

100 PAJ

65 SJ

The bike starts great, first or second kick all the time, but no change when turning fuel screw. I think I need to go down on the PJ. The bike snaps to attention and goes like a bat out of hell to about 2/3 throttle and then stops pulling and starts to stumble at WOT. Seems like I'm hitting the rev limiter, but I don't think so. Also the bike pops on decel, a sign of lean correct?. I was thinking of going up on the MJ to a 170 and try that. Any opinions !!!!!!!!!! I think I'm close

I thank you for any help you may have.(and yes I have been reading everything about jetting)

Pete :D

That sounds like it's rich on top. The YZ comes with a #162-165 main, maybe go down instead.

With a #48 pilot, keep the fuel screw in the range of 3/4 - 1 turn out only, no more than that on the '00-'02 WR.


OK.....I will try that -- A 165 is next. But, when I set the bike to a high idle and turn the fuel screw in the engine never hits a point were it wants to die. So I thought the PJ must be to big -- is this wrong? or is it the large MJ fooling me? Thanks for all your help JD. And for the jetting guide, it help me understand more of whats going on. :)

Pete :D

agree with JD. infact i'd go down through to 160/162 MJ. if it's your needle clip it's only because the MJ set it up for the fall. with the MJ corrected the needle should come right.

you can turn the PS right in when the PJ/PAJ ratio is to cock. i know what P Burns says but i've never held any store by it when jetting. as said before with one or two exceptions (and this is one) PB is right.

you basically have too much fuel and air with the 100/48.

it's taken months to get everyone there but go with 40 maximum and preferably i would go with 35/38 PJ as you lean off the jetting and get it spot on. don't forget a PAS and get your ratio right.

if you read jetting Qs you'll know that near the 35PJ the idle knob had to be turned out ONE WHOLE TURN. i'm hoping the significance of this isn't lost on anyone. right from when you set the "air screw" on your first yamaha FS1E when you got it right and the revs shot up; you turned the idle knob out to get the tickover (idle) down.

you'd arrived :):D



OK........I will contact SUDCO and order me jets today, but I have a question about the PAS. How is this adjusted? I don't remember seeing anything on setting the PAS. I will look back at jetting Q's and research some more. Thanks for pointing me in tne right direction. :)


the S in PAS stands for screw :)



Yes...I ordered a Pilot Air Screw from SUDCO today, but he called it a ajustable air screw. I hope that was the right part :) . Also, I assumed since it is a screw thier is an adjustment to be made and I don't remember reading anything about how to adjust this. Please correct me if this is wrong. But be gentle :D I will be off reading jetting Q's. Thanks

Pete :D


Taffy supplied me with the jetting in my signature. My old jetting was based off the EKP needle and was very similar to yours. The bike was very finicky at lower temps (ambient and operating).

I just put in the needle and jets yesterday and could only ride around the block. I'll be getting out this weekend and will report my results. But so far, the bike starts just as easy as before, is much cleaner running (no popping or sputtering), can be fed throttle when cold (and will rev immediately) and is pulls very even throughout the throttle range.

I know it means buying more jets, but the EM_ is better than the EK_ needle. Might want to do the AP mod also. If you need to buy the collar for the pump rod. Go to any hobby store that sells RC airplane stuff and buy the wheel retaining collars. For $1.50 you'll get four collars and a wrench.


Man I can't wait :)


I will wait for your results. Buying more jetts is not a problem if I can get this done right. Its only money -- right :) Good luck and thanks for your input.

Pete :D


Sorry...that did'nt work like I thought. Is this what I should be looking for?


just thought i'd issue what i consider to be the correct pilot air to pilot fuel ratio's. these settings should work with the pilot screw at 1.5 turns plus or minus .5 turn.

they aren't overly affected by the richness of my needle straight (**M) nor by the standard euro pipe, but add the two together and chuck in sea level as well you can see that some of these figures may change.


48 110-125

45 100

42 85

40 75

38 65

35 55

there is the possibility that all the PAJ figures on the right could come down 10.

quite honestly if you're within 10 you'll be just about ok.

if you're a little lean on the pilot with say a 40/100 you will find a little rough patch of revs at 1/4 throttle in second.

if you're a little rich with say a 38/55 like i'm running now it will affect your tickover and make it rich on choke but will clear as you move off.

if you've reduced your APJ to the recommended minimum you'll still be able to get through but i recommend that you disconnect it for any testing and then reconnect at the end to get your snap in first and second gear back.

otherwise your results will be confusing.

the needle doesn't appear at first to affect this area too much but the MJ does. that means that once you are reasonably happy with a couple of mods you should go for your MJ/MAJ tests.

the more changes you make at the top end, the more you'll have to make at the bottom afterwards. it's your choice!!!

the needle taper start will slightly alter your pilot area jetting, but only slightly.

if having got the MJ right by lowering it (say 170 to 160), you'll likely have a lean needle area. this is because the needle gets it's supply from the MJ and that supply is slightly reduced.

so a lowering of the MJ will be accopanied by a lift of the needle by a clip. this in turn means that the taper of the needle starts sooner and richens the very bottom. not by much, as said. but two needle clip changes will require a change of pilot air and jet.

to conclude my recent testing. i got down to a 35PJ. i then lowered the MJ from 160 to 150 and had to put the PJ up to a 38 again due to leaning the whole circuit. then i lifted the needle two clips and now start the taper 2mm sooner. now that is a lot of extra fuel.

i could have lifted the needle first the two clips but that isn't what i was feeling back from the bike at that time.

anyway the PJ is now getting that extra help from the needle taper start and it's ready to go back to 35PJ. this will lean the start and tickover again (i haven't moved the PAJ from #55 although i should have done). this will mean that the ratio will correct itself again and the choke ( also called starter) jets should be ok again after all.



Pete :)

this is the article i put in a few days later

"as i hope this will be archived someday i thought i'd mention that with reflection i think that my final set up of 55PAJ/35PJ could be improved to 45PAJ/35PJ.

it's just one of those things that you reflect on and run through your mind. all my mods came from just "chewing on it".

my chart therefore reads;








this just about makes the gap 15 of PAJ to each PJ so this makes it a kind of easy to remember rule of thumb.

remember that the PAJ is there to drag the fuel out and you can only soak air with so much fuel before if you need more fuel; you need more air first. thus the ratios.

an element of the pilot circuit ratio works when you start the bike (40%), but just as you move off the bike wants to draw way more fuel/air than it could get past the needle so you must alter the PS to dictate the curve on this. so;

PS 1 turn out

starts with 'X' fuel/air and doesn't really get a lot more as you move off.graph flat.

PS 2 turns out

starts with X fuel/air but as you move off the mixture richens strongly. graph steeper.

so the PS helps you dictate what you get most of all from idle (hardly any help in or out)to 2-3,000 revs where it akes a big impact.

so what has the biggest contribution at tickover?

i'm guessing but i'd say that;

needle straight is 40%

PAJ/PJ is 40%

PS is 20%

the latter two though, are meant to be there from opening throttle to 2/3,000 revs and so we need to set the bike on idle with the needle diameter.

this as many of you know is the last suffix in your needle. so to richen the mixture at tickover we would for instance go from an EKP to an EKN which is thinner and passes more fuel.



i've modified my old article-even i can't make sense of the original. for those of you trying to visualise it; try this.

in your mind draw an upward sloping line 6" (nice'n shallow) this straight line is the optimum fuel line for your bike. now all you need is to start another line at the start and go straight and flat for 1 1/2". now a third line, this time from the start point and rising more steeply than the long line (1 1/2"). use a colour pencil to fill in an arc betwen the two shorter lines. it should look like a tilted up megaphone with a line coming out the middle.

now you've got it!

what it means is this;

the pilot screw can do little at idle. the mixture here is set by your needle. the PJ/PAJ are here to work from the moment you open the throttle to mid revs. you don't want to have it setting your idle, it's got more important work to do. SO YOU SET IDLE WITH THE NEEDLE STRAIGHT. the PC then does it's bit at low revs, the needle and MJ chime in later.

so what about the different PC ratios? what does 45PJ/75PAJ do compared to 35/45.

lets try 45/75 instead of the 35/45 we just pulled out...

well the tilted megaphone still exists. same angle, length, tilt the lot EXCEPT THAT IT'S NOW MOVED VERTICALLY 1/2" ON THE PAGE. so now the idle is rich (and you still can't alter it much with the PS).

two PS settings:

0-1 turn out

if you look at your graph the lower flat line still cuts across the ideal "fuel line" you drew so you're ok at say 2,000 revs. the problem is that it is chucking it in (rich)at idle and the PS makes no difference, also, that lower flat line went UNDER the "ideal fuel line" so at the extreme top of the PC's range when hitting the throttle in second at 15mph/3,000rpm we have a flat spot.

1.5-2 turns

as above we're rich at idle and not much we can do with the PS. now watch that fuel graph (yyeeeehhhhaaaaaaa)! it started above the IFL anyway and now it's in vertical orbit!!! this bike is rich. luckily the only thing that happens is that we get a slight "stumble". ever been there boys?

some of you will say; "well if the needle is 40% of idle (tickover) the PC is still the other 40% and the PS is 20% so we can use the PC to change idle surely?

ok, true but what a waste!!! the PC wants to be at around 35 to 38PJ and have a PAJ setting to suit (PAJ 45 for the 35PJ and PAJ 60 for the 38PJ) we then use the PS to get the angle of the curve right and to actually start the bike that leaves the needle straight!!!

another analogy for this is that we have a 50 gallon drum and we need to get it to the line at the top we might change all the PJ's in the world but the level in the barrel only goes up or down 1". not a lot is it? so the needle straight doesn't have to change drastically to "top it up".

i hope i've explained this well this time.


[ April 20, 2002: Message edited by: Taffy ]


Thanks. I think I will wait for Bill to get back with me with His results and then I will jump to the EMM and change my MAJ also. Thanks for your help and I will report my tests. I just need to find some time when I'm not Coaching Soccer....Damn Kids :) I'm kidding I love it.


Hey Pete,

Sorry for the late reply. Glad to hear you're happy with the forks.

My EMM is backordered at SUDCO -- damn it. I hope it will not take long.

Bill - How did the jetting work out?


Unfortunately it didn't, it rained. I hope to get out on Thursday.



i wondered where you got too!



I dont know how to describe the difference but the jump I use to bottom on -- not no more, bike uses alot of travel and settles nicely at the end, great balance. And in the woods it felt plush. It soaked up tree roots, rocks, everything. I wasnt riding really hard because we had the kids, but I can't wait to give them a good test. I may call you to ask some general questions. Again Thanks


Good luck and wait to here from you.

Pete :)


Is the PAS just a spring and a needle with some threads on the end? This is what SUDCO shipped me. If someone has the SUDCO part #, that would be great. Thanks,

Pete :)


it's a screw with a hole down the middle and across the end.


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