Taffy, Jet Ratios & Altitude?

old novice

if you think they took a long time to read!

A) spare a thought for the testing

:) spare a thought for the two friends of mine called left and right (they share the same double-barrel sirname of 'index finger')

there is no relationship worth counting between the MJ/MAJ area and the PJ/PAJ area.

as i understand it the M needles are too rich if they're not at sea level. a N for sure and higher still it needs a P from what i can gather.

several euro boys encountered problems initially and nearly lost the faith but after a while got it right. i believe the same could happen in the states but the feedback has at times been very poor.

i gather that the later carb with a P needle is ok off a closed throttle but the early carb with a P creates a hesitancy just off idle. doesn't matter how often you say it though, there are so many P needles out there that you'll never stop people now. it's endemic and i've done it all and seen most of it so i ain't fighting no more. the results prove it.

as far as the MJ/MAJ and the needle go, well that's interesting because i've always maintained that i was setting the fuel curve to match the fuel curve the bike needs. but i would think that the WR timing falls away even earlier than YZ timing and therefore it needs bleeding more. but the carb may be compensating for itself. fatc is though that one or two say it's better and if nothing else it allows the needle to be lifted and other mods to be made.

that as i've said to others is for them to find out. but as you'll have read in jetting Q's i gave up a whole day to just these tests and i doubt if anyone has done anything like it elsewhere bar JD.

in answer to the altitude thing an EMN or EKP will do the job. or the equivelant D series.


A) spare a thought for the testing

I now have a system for swapping the various carb parts and still have not tried as many combinations in one day as the tests you did in Jetting Qs. I do understand the time involved, make no mistake.

:) spare a thought for the two friends of mine...

Thank goodness I can type with all fingers. :D

After reading all of this and LarryCO's response to another post I am now considering adding an E__ needle or two and a 160MAJ to my parts order as well as a couple smaller PJs. This should keep me busy adapting what I have learned here to this altitude.

Old Novice...

Taffy's point is to be taken...in that testing on your own to what you feel works best is the most important thing. I've obviously told you what I feel works best for me (without me completely "splitting hairs"). There still may be a better setup out there, but after what I deemed the proper amount of testing, I'm sticking with the 38PJ/65PAJ/EKP#3/150MJ/160MAJ setup that I mentioned earlier (for Rampart sort of altitudes).

Didnt really spend much time on the 160MAJ decision...just took Taffy's advice on that one...or, for that matter, D series needles...so if you want to do some testing around that, please post your results accordingly.

Good luck...and keep us notified on your results...


Taffy, while waiting for my carb parts to arrive I have been re-reading "Jetting Qs" and other posts relating to adventures in jetting. All of this information has me pondering a couple of questions.

First, what effect if any would you guess altitude would have on the PJ/PAJ ratio relationship you charted in Jetting Qs? (note that I live at 6000+ feet and go up from here to trail ride)

Second, I believe you ended up with a 160 MAJ in your most recent combo. Did you discover the same type of relationship between MJ/MAJ as you did with the PJ/PAJ and does the needle taper affect the MAJ choice? I ask this last part because you were testing E__ needles for the majority of the time. Again, how would you predict altitude effecting the choice of MAJ, or would it even be a factor?

Those threads were work to follow and I am still not sure I have a complete grasp on what was discovered in them. Well worth the time to read though. Thanks all who participated/experimented.


I have slightly different jetting (see signature). And I am happy with the performance I have pulled out of the machine. Someday, if we are ever in the same area, we ought to test ride each others bikes. I would love to see what difference the slight changes have made, or, if it just depends on the personality of the machine itself. I am leaning towards the second theory.



Sounds good to me...I'll be that vortip has something to do with it as well. I'd like to hear the difference in sound a vortip makes...it's been on me "to purchase" list for a while now...


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