02 Lean jetting results

4 replies to this topic
  • okieguy

Posted May 14, 2002 - 08:40 AM


Installed the following last night

emm - clip#4

Bike has all the free mods including yz timing.

Seemed like it started a lot easier but once warmed up had the stumble when you crack the throttle.

Going to the track tonight to give it a good riding but anyone have any idea's on the stumble.

My old jetting was:

DRN - 3

Bike ran strong on bottom & mid with no stumble but felt like it hit the rev limiter to early. Also would foul plug if not careful.

Thanks for any coments or sugestions.


  • Taffy

Posted May 14, 2002 - 08:56 AM


you have effectively gone 10 richer on the MJ.
why? well let me explain.

a D needle needs to be 5 (in my opinion) richer than an E needle coz the D needle is so fat that it doesn't pass fuel too well. so that 165 should be a 160MJ with the EMM, OK? the next thing is that you've gone to a 160MAJ which means that your MJ should come down 10. so now that's a 150MJ.

so i would definately go down to a 155MJ and you can feel comfortable that that will be ok.

your EMM needle is about 3 clips richer than your DRN there is so much less metal.

by coming down 5 on the MJ you will have effectively starved the needle of some fuel so that you're now only two needle clips too rich.

so you're not too lean-you're too rich, ok!

once again;
down 5MJ to 155MJ
drop the needle once
drop it again (i should think)

the testing is up to you. you're responsibility. for the MJ test get it flat out on the ROAD with at least 14/50 gearing (the taller the better) i had 15/50 and 15/48.

find a long shallow gradient. flat out in top and roll it off and WOT again immediately. that is MJ. the 155 will rip harder and faster.

for the needle test SAME AGAIN except that this time you close the throttle and say "one" then WOT again.

do come back and let us know how you got on.

APJ set up?
year and model?
YZ or WR timed?


[ May 14, 2002: Message edited by: Taffy ]

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  • okieguy

Posted May 14, 2002 - 09:26 PM



My altitude is about 650'

When you say drop the needle that is raise the clip or lower the clip?

I think I am a little lean and should richen.

Thanks for your input.


[ May 14, 2002: Message edited by: okieguy ]

  • Taffy

Posted May 14, 2002 - 10:03 AM



i've just spent so long on the phone whilst editing the post that you had replied in the meantime!!!

now you've read my post you'll trust me when i say you're RICH (well bloody poor actually!!).

never talk of what you do to the clip talk of what you do to the needle.

drop the needle. you think about the clip!!

good luck and let us know how you get on!


  • okieguy

Posted May 15, 2002 - 05:04 PM


Rode the motorcross track last night.

Got the stumble out by turning the ps in to 1/2 turn.

The bike ran better than it ever has.

Still going to try to drop the needle one and go the 155mj.

Thanks Taffy



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