Jetting Qs



244 replies to this topic
  • James_Dean

Posted December 06, 2001 - 09:38 PM


I wouldn't suggest you change other than experimenting with the main jet. Factory racers look for what you have. It's up to you... The YZF uses a #162, the CRF a #175, and you're right in the middle.

EMN is the same needle shifted a clip leaner. EKP is the other twin, splitting hairs on the needle diameter (.0004 inches)- leaner, 0-1/8 throttle range jetting.

-What's with the "octopus removed"... you have a 2000WR? :)

  • Harold_in_So_Cal

Posted December 07, 2001 - 01:39 PM


octopus removed- when I first got the bike I printed off the instructions from the tech page and gave it to the mechanic setting my bike up and asked him to do it. Am I missing something?

  • James_Dean

Posted December 07, 2001 - 02:16 PM


The 2000WR never came with the octopus hoses etc. I hope he didn't charge you for removing it! :)

  • Taffy

Posted December 07, 2001 - 10:05 PM


:) :D
:D :D
:D :D :D :D

i do wish i was wearing my kidney belt-just for reading TT!! aahhaahhahahhhahahhahhahhahhahhhhh

beautiful, absolutely beautiful.

can anyone remember the guy that wanted to put a hairdryer in his airbox so it would act as a turbo!!!aaahhahhahhhhahhahhahhahhahahhhahhahahah

sometimes this site is just so beautiful.

Taffy

  • Harold_in_So_Cal

Posted December 08, 2001 - 08:22 AM


Thanks. I'm glad I can provide some entertainment value. :)

  • Taffy

Posted December 09, 2001 - 06:29 AM


just got in from testing.

the bike started with 150MJ, 160MAJ, EKPc4 (=EMMc5 but two sizes larger on the straight), 38PJ, 55PAJ(S), 1.5 turns PS. no APJ

the bike is in the papers this week so i didn't take it on the land etc but it was all about snapping the throttle.

the only difference to previous rides was the EKP needle which is up two sizes on the straight.

test A
this is the starting on choke. took two kicks and then off it went nice 'n steady chuffing away. with the EMM it's revving it's nuts off and then 8-stroking after about 30 seconds.

test B
the bike is dead for the first two yards and then goes. this can fairly and squarely be put down to the needle straight. so it's too lean. accepting that this was to be an APJ test i think it's still valid to say that the bike didn't like to start quite as well. but it's close and deserves a longer appreciation.

i'm now pretty sure that the EMN would be the right needle

first-third test
rod chopped in half and 2mm removed. tried all kinds of delayed start and in the end decided that i liked it to be there immediately. the way to tell is to look at the drilled hole in the black rocker arm. this is actually OVAL shapped and the rod was best at the top, in other words at it's full length.

fourth-sixth test
the actual stroke is about 3mm to look at. by lowering the block connector bit by bit i stopped at 1mm of travel and that was fine.

this gave me snap from closed in first and second. in third i wouldn't expect to go back to a closed throttle.

it may come down even more. to say .75mm or so.

as i've said previously there is no APJ at higher revs so this is for first and second gear snap.

the bike was generally misbehaving at closed to 4/5 yards i think due to the EKP needle i'd put in.

what i like about this mod is that if i want to check my jetting i can put a split pin in the 1mm gap and render the APJ ineffective while i sort the jetting out.

Taffy

  • Speeder

Posted December 09, 2001 - 07:33 AM


You guys are the tinker kings, I love it.
I've been following this for some time, using the posted info to guide my own jetting selections.
I'm driven to ask, and I'm sure I'll get an opinion.
My jetting is a bit different from what I am seeing. So, is it because of the combination of my pipe, final drive ratio, and riding, or does my bike run like a dog and I don't know it?

Here you go:
2000WR, YZ timed
Pilot #42 at 1 turn
EKP at #3
Main #185
15/48 drive sprockets
(I ride desert approx. 3-4,000 ft)

By the way, no choke required until 45 deg F, never fouled a plug, and EKP #4 ran badly.

  • James_Dean

Posted December 12, 2001 - 01:24 PM


Taffy,

Good test results and explanations. The tests are close to matching mine on the '00WR. A 1mm stroke was a good compromise to none. That misbehaving of the EKP left me with a bigger pilot jet, I'm sure of it. The '01YZ426 went 1/2 clip richer at EJP#4 too.

Is this thread ever going to end? :)

James

----------
A 185 main jet sounds way too big. EKP#3 is in the vicinity, try #4 again with a much smaller main, like #170.

[ December 12, 2001: Message edited by: James Dean ]

  • Taffy

Posted December 12, 2001 - 03:15 PM


mateys

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.

PJ PAJ
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.

Taffy

  • Taffy

Posted December 13, 2001 - 11:17 AM


ok<p>i've been out and done a little test again today and think i've finished. but then i said that last week! <p>so after the above post i went out and dropped the PJ to 35 from 38. i also swopped the starter jet from the #62 that was in it to the only other one i have which is a #60. this i hoped would really help starting and the low end. <p>i also dropped my no expense spared APJ mod from .045" (1.1mm) to .032" (.8mm)but i'm giving you absolutely no clue as to how you can be so accurate. you'll never guess, it's a secret [image]images/icons/grin.gif" border="0[/image] <p>i also put the throttle cable cover back on as this is it. put it all back together.<p>started first kick, went straight to steady revs and didn't move up or down. perfect!!<p>choke in after 40 seconds or so and the tickover was high enough that i had to turn the idle knob out 3/4 turn. clearly the bike loves this set up. <p>the flywheel weight is off it now so my signiture is getting shorter and shorter [image]images/icons/frown.gif" border="0[/image] <p>test ride it on sunday but you know it's going to work doncha [image]images/icons/grin.gif" border="0[/image] [image]images/icons/grin.gif" border="0[/image] <p>Taffy

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • James_Dean

Posted January 04, 2002 - 11:48 AM


Back to the Top!!

This thread should be archived for future reference.

James

  • Taffy

Posted January 04, 2002 - 02:06 PM


then while it's here i ought to mention that i put the pump (APJ) movement down to just .024" (.6mm) and it was an improvement. what you must be sure of is to check it without filleting all the fuel.

for these tests to work right it's got to be fully primed and with no air in the system. this will only happen after a regular run or use when all thew air is bled out.

Taffy

  • Taffy

Posted January 15, 2002 - 11:01 PM


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. <p>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". <p>my chart therefore reads;<p>PJ/PAJ
48/110-125
45/100
42/85
40/70
38/60
35/45<p>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. <p>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. <p>an element of the above pilot circuit ratio works when you start the bike, but when you move off the bike wants to draw way more fuel/air than it would get past the needle so you must alter the PS to dictate the ceiling on this. so;<p>PS 1 turn out
starts with X fuel/air and doesn't really get a lot more as you move off.<p>PS 2 turns out
starts with X fuel/air but as you move off the mixture richens strongly. <p>so the PS helps you dictate what you get most of all at lower revs. <p>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%<p>the latter two though are meant to be set for open throttle and the first 2/3,000 revs and so we need to set the bike up at this point (idle/tickover) with the needle diameter. <p>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. <p>Taffy

  • mattnohiohills

Posted January 18, 2002 - 04:45 PM


Ok, I am going to start tinkering with jeting and needles. Carb is stock except for the throttle stop. I plna on De-octopusing the think and doing the bk mod. The question is.....
What jets and needles should I buy before I get started on this. I don't want to be running to the bike shop every other day. Anyone have any suggestions where to start? I am at 1000ft 20-30 degrees now, summertime highs, 90's
ANY HELP would be MOST apreciated.

  • Taffy

Posted January 19, 2002 - 06:33 AM


matt

this is an old thread dedicated to jetting by one (or two ) people. i would recommend that you start a new thread if it wasn't for the fact that your question has been answered a zillion times already. please do a search and type "jetting" or EKP.

Taffy

  • Rich_in_Orlando

Posted February 26, 2002 - 06:57 AM


Hello, Taffy

  • gerry

Posted February 26, 2002 - 07:56 AM


After a year of riding my 02 WR426 i've decided to cleen the carb as bike is not returning to idle quickly, I'm thinking about re jeting but the bike runs perfectly for what I use it for i.e tight woods and low down power poping wheelys etc the only problem I have is that it pops and bangs on the over run, I have a whites E series pipe no air box cover and run a
needle @# 4
Main Jet 165
Pilot Jet 42
Main Air Jet 200
Pilot Air Jet 75
I know this has been asked before and you guys must be hacked off with guys like me asking the same things but how can I improve power just a little with out going to mad on the jetting possibly to stop the popping on the over run I don't want to spoil what I've got as the bike never stalls and always starts first kick

  • dieseld

Posted February 26, 2002 - 08:16 AM


Gerry -

I had the same thoughts you did, my bike ran good and started easy, but popped on decel.

You need to take a leap of faith here and go with the recommendations that these guys have put so many hours into tuning. Your bike will still start easy and not stall, and it will run better than you thought possible.

Damon

  • James_Dean

Posted April 08, 2002 - 02:38 PM


Back to the top for another look.

-----------------------------------------
I have run a few tests on my '02 400EXC for comparison of the pilot jet/pilot air jet ratios.

Running OCEMM#5, the following were tested.

PJ/PAJ-
#48/100 (stock)
#45/75
#42/75
#38/65

These all ran with god idle, quick starting and no signs of too lean or rich with the fuel screw near 1 1/4 turns out. The smaller pilot jet settings are especially clean running and smooth. In some ways feeling like a streetbike jetting. I'm going to go back and look at #45/85 also. It will take some time, but I plan on coming back to take another look at this again. Thus far, the #42/75 was most crisp and responsive.

This carb is like the '98/99 YZ without the air cut/bypass valve of the WR. Also looking at a OBDRN needle. The EXC has a quieter exhaust, more like Taffy's Euro WR400 was. It may be factoring into this too.

James

  • Taffy

Posted April 20, 2002 - 12:48 AM


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;

PJ/PAJ
48/110-125
45/100
42/85
40/70
38/60
35/45

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 from idle (hardly any help in or out)to 2-3,000 revs where it makes 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.

Taffy"

_____________________________________________


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 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.

Taffy

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




 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.