Sea level jetting for a '99 with YZ timing?

60 replies to this topic
  • Taffy

Posted March 20, 2002 - 12:05 PM


you're welcome mark. easter would be a good time. in the week up to GF or the week after EM would be fine.


  • huskyrider

Posted March 20, 2002 - 06:14 PM


Could you let me know what your final jetting is? I'm in SE Texas at probably the same elevation,humidity,and temperature as Orlando.
I'm fixing to go to YZ timing and want to jet as closely as possible from the getgo.
Thanks to you and all the guys such as Taffy and JamesDean who've spent all this time dialing in the jetting, I'm hoping to get mine real close right off the bat.

Taffy or James,
Would I be correct in assuming that this is good with YZ timing only, and that if I go back to WR timing I'd be better with a "d" series needle.
My current jetting is stock with not quite a second of accelerator pump shot. With this jetting should I be able to cut my pump shot down to less than a half second. I left it a little long thinking I created some leaning effect with the baffle out and the airbox lid off and a little extra gas couldn't hurt.(it made since to me, but what do I know)

  • Rich_in_Orlando

Posted March 20, 2002 - 06:40 PM



The carbs on the '99 and '01 models aren't the same. A friend of mine who I ride with has an '01 has his bike jetted stock with all the free mods , and I have ridden it. It needs no modification. But his is WR timed. How the '99 settings are related to the '01, I don't know.

But here's what you asked for:

160 MJ
160 MAJ
35 PJ
55 PA(J) Screw (3/8 turn out)
60 SJ
EMM clip 4
PS 1-1/2 turns out
tiny (~1/2 sec) squirt of the APJ

[ March 20, 2002: Message edited by: Rich in Orlando ]

  • James_Dean

Posted March 20, 2002 - 07:19 PM



This setup will work with either timing. I ran the EMN (almost same as EMM) in my WR with WR timing and found big performance gains at mid-throttle. The difference is how the bike responds to throttle input. Peak power remains the same. The Dxx is tractable and stays under control only because it is weak in the mid-range (IMHO) unless the clip position is set extra rich for down low power. Then it's a blast too.

The Exx is the "standard" Keihin needle taper for the FCR carb.


  • sbohanon

Posted March 21, 2002 - 03:43 AM


taffy, what is your elevation, air temps, etc. i would think they are similar to rich in orlando. in the past i have stated a reluctance to drastically change my jetting since all seams fine, however an increase in fuel economy would be real nice. i plan to do the bk mod soon, found a 2mm shaft collar to do the job, and will try the ekp needle with a 165 main jet. i am in the process of obtaining the emm needle (i realize the needle and main shoudn't increase the fuel economy). my question is in leaning out the pilot circuit. being in the northeast our temps and humidity during most of our riding season averages between 30-80 degrees and humidity is 30 to 60%. how might this effect your research in the leaner pilot circuit? i have a 50pj with stock paj.

  • Bill

Posted March 21, 2002 - 04:13 AM



I've ordered ALL the jets from Sudco including the EMM needle and Pilot Air Screw.... not sure if I'll use it (PAS). I also ordered one step higher and lower for the PJ and MJ.

You might want to try the EKP configuration in my signature. My only complaint is starting the bike on really cold days. You know, like the day we met at RC :)

The part# for the needle is N427-OCEMM


  • sbohanon

Posted March 21, 2002 - 07:27 AM


bill, hows it hangin man!! been to rc lately!! a friend of mine won the 4-stroke class and finished 6th overall at the harescramble there 2-weeks ago on his 426. i couldn't make it, it was the wife b-day.

i haven't had any problems starting my bike in the cold, 6-8 kickd with no blip. i was at flying dutchmen last week and it was 34 degrees, she started right up.

any improved fuel economy would be great as i didn't have to gas it up for 8-laps. if i can ever get that elusive 9th lap i would need it. i don't care for the oversize tank and would rather carry a quart of gas with me on a belt.

we have to get together this summer, lets talk. i still hang with npuza. we raced at buddscreek back in february and are going to the arenacross at the fu center.

  • Bill

Posted March 21, 2002 - 07:37 AM



My jets should be here today and I plan on riding a week from this Saturday. Not sure if I'm going to RC or not.

Mike68 is coming down from NH to ride RC on April 20th and 21st. Him and some buddies are bringing a RV to stay at the track.

Hope to see you and Nick there :)


  • Taffy

Posted March 21, 2002 - 08:58 AM



i live at sea level and i think the numbers are good up to 3-4,000 feet. but that doesn't mean you shouldn't try the settings, it just means that they'll be good but need a tickle or two.

the humidity robs you of oxygen which is a bit like altitude i suppose.

the idea is that if it pulls cleanly off the bottom; it will use less fuel and so you can gear it up slightly. then you use less fuel again.



  • Rich_in_Orlando

Posted May 16, 2002 - 02:22 PM


Well, I finally got around to the PA screw adjustment Taffy recommended. I screwed in the screw to 1/4 turn out, which is equivalent to a 45 PAJ. It definitely cleaned up the low end vibration Taffy wrote about. It also seemed to reduce the time the choke needs to be on.

Also, since the weather's turning hotter and more humid, the bike's been running a little rich lately. Symptoms were a "blubbering" (as I've seen described elsewhere on TT) and a little hesitation at mid throttle. Honestly, I wasn't sure if it was running rich or lean, so I started by richening up the EMM needle clip position. Starting at the 4th clip, I raised the needle to the #5 clip. The bike ran worse than ever! It was sputtering, blubbering, and kind of missing at mid throttle. So, I figured I had went the wrong way. I lowered the needle to clip #3 and it cleaned up nicely. But since it was clean in the middle, a little hesitation became evident at full throttle. To fix this, I leaned out the MJ one increment, from a 158 to a 155. That did it! It's running like it should again. As as matter of fact, now that the bike vibrates less, it almost feels like it's going slower, except for the fact that I had a hard time keeping the front wheel down while accelerating hard. I had to lean forward just to keep both tires on the ground as much as possible during the acceleration tests.

So now my jetting is:
155 MJ
35 PJ
60 SJ
EMM #3
160 MAJ
45 PA screw
fuel screw 1-1/4 turns out
1/2 sec. APJ squirt

[ May 16, 2002: Message edited by: Rich in Orlando ]

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  • Taffy

Posted May 16, 2002 - 09:55 PM


i forget who it was with but about 5 months ago i tried to get a rider to just say "how long the choke was on". i like mine to be on about 30 seconds because when it's off the bike just sits there ticking over nicely!

less than that and i haven't got my gloves on. no only joking :) what i meant was the revs drop heavily and the bike isn't ready to ride.

your jetting sounds just how i'd imagine it to be if i lived over there.

just let us know what your choke is like. you may find that the bike is even crisper by dropping the needle one. otherwise from what i know you're spot on.

you'll ride it for days and spot little things perhaps? let us all know. personally it's really pleasing to have helped a regular contributor who puts up plenty of feedback.

well done!


[ May 17, 2002: Message edited by: Taffy ]

  • okieguy

Posted May 18, 2002 - 05:00 PM



Have you checked the color of the plug, I am running close to the same jetting as yours (just a little richer) and looked at my plug and the insulator is very white.

It has me a little concerned but the bike runs great with the leaner jetting.


  • Rich_in_Orlando

Posted May 18, 2002 - 05:10 PM


Nope, I have not done a plug test since going leaner. I've been relying on the seat of my pants for jetting feedback. All I know for sure is that when I richened it even just a little, it ran like crap and when I leaned it out, it runs perfectly. (BTW, I think the insulator should be white no matter what your jetting is. It's my understanding that it's the color of the electrode that is important.)


Posted May 20, 2002 - 04:21 AM


The color of the insulator is what you read, not the electrode. The insulator should be a nice BRONZE color if your jetting is Spot-ON, make no mistake WHITE is Lean. It is the Degree of White that should concern you. Holes have been known to be burned in pistons and valves destroyed in overly lean conditions. Lean jetting will cause your bike to scream with power, but really at what cost. I was going to lean out mine until I pulled my plug Friday night and read it. Nice and BRONZE. Runs Great, Front Wheel Lofts on Command, six foot rooster tails out of the corners and I can run with the head of the pack. So I figure why make any dramatic changes. I will however drop my SJ down to a 55 to compensate for removal of the ACV. Mine Starts perfectly, 2 kicks when cold because of the ACV removal, But always on the 1st kick when warm.

I'm gonna watch you guys for awhile and see if anything adverse happens before I make anymore changes.

Bonzai :)

  • Rich_in_Orlando

Posted May 20, 2002 - 04:58 AM


One of these days, I'm going to take a look at the plug color on the insulator. I've always looked at the electrode so now I know that's been a waste of time! :)

I've probably got close to a thousand miles of hard riding on my bike since I've leaned it out and no adverse effects so far. Does anyone think piston damage could occur from over-lean jetting without any other outward signs of overheating such as coolant boiling, etc.? (My bike has exhibited none of those types of symptoms.)

Yamakaze, did you get the swingarm and linkage bearings replaced?


Posted May 20, 2002 - 06:23 AM



It took me about 4 hours on Saturday to get everything done. MXTUNER (Thanks Mark) pressed my Steering Stem Bearing on for me and serviced my forks while I waited. I went riding on Sunday, Man what a difference, Can't wait unti the first when I get my Scotts Combo. That should allow me to loosen my death grip up on the bars.

My concern for the piston damage is because I've seen it before in Street Bikes that have been overly leaned out. My neighbor did it to his Virago and didn't have a clue until he lost ALL compression. No warning...Pinging..Knocking..or overheating...

Bronze or even Grey is ok...White is deadly when it comes to an internal combustion engine....Like having a high intensity torch aimed at the top of you piston.

Bonzai :)

  • Taffy

Posted May 20, 2002 - 01:43 PM


how many times have i got to say it-DON'T LOOK AT THE PLUG.

break the exhaust at the mid point and look into the silencer. if you run unleaded the only plug colour you'll get if it's in the ballpark is WHITE :D :D !!if it's rich it's white and if it's leqan it's white. ivory, ivory.

even if you run leaded it may not give you a colour. everybike is different but one day i'll tell you of the hardest ever learnt lessons on this you can get.

go by feel :D :) it's the best way.

hole a piston? bollocks can you! the compression of these is the equivelant of an old indian, no the indian was more likely to hole a piston than the yam!

you would have to be totally negligent not to recieve the type of messages the bike would give out. it would pink, it would stutter, it would rattle, it would give off excess heat. even the exhaust note and the colour of the tailpipe would be different.

it gives off a spatter as in paint around the exit. don't panic boys, stay calm.

remember the bike will tell you if it's lean. your more likely to have a big end, small end go BTW than hole a piston.

(Taff now gets off his soap box to field some old low flying cabbages!)



Posted May 20, 2002 - 02:41 PM



As you are well aware, I hold your jetting prowess in high reguard, and agree about 95% of the time, However I must beg to differ when it comes to your "Don't Read the plug" montra. You appear to be the only person on this big blue rock preaching this message....Kind of like Jim Jones in French Guyana....(I saw that Aftermath First Hand). As well also, I have seen the results of overly lean jetting in the case I mentioned earlier. If I had not personally observed the head being removed and the small hole and concave surface caused by "directed Ignition" , Yes the pipe showed signs of heat stress at the outlet, (But so does the FMF header on my WR)....Note carefully that I have not said that your jetting direction is wrong, I simply made a point that a white plug indicates a extreamely lean setting...I think my Degree in applied science (Automotive Maintenance) allows me to say that. On many points we agree, however on plug reading we do not. And so it goes. No rock throwing, just a difference of opinion.

Additionally My WR runs great thanks you your's and JD's recommendations well over a year ago. Just for $hits and Giggles I uncaped my exhaust tonight just to take a look (I couldn't resist) the interior of my canister is dark grey, almost brown. and my plug is a beautiful bronze with no carbon build-up on the electrode or around the bottom of the plug. My experience tells me that my fuel delivery system is just about perfect. The power is excellent all the way through the throttle range, no glitches and no hesitation, The beast launches off the line like a rock throwing cave dweller (Just ask the guy's that are unlucky enough to get smacked by my rear tire)
The only thing I don't like is the richness on the SJ which I will remedy next week with a 55 SJ.

Once again no arguement from me, just a difference of opinion.

Bonzai :)

  • Ynahg

Posted May 20, 2002 - 09:31 PM



Do you have any idea where I can order the following parts from here in Europe (Belgium) :

160 MJ
35 PJ
60 SJ
160 MAJ
PA screw

I heard these settings worked quite allright :) .
I've tried to order them at my local yamaha dealer but he doesn't have the part nrs.

If I understood things right the stock DXM needle isnt' a bad issue ? Or should I go for the EMM anyway ?


  • Taffy

Posted May 20, 2002 - 11:04 PM



allens performance R & D is on 01949836734

their website DOESN'T have a e-mail address so you'll have to call. they won't need the part numbers, just name the bike.



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