Taffy's jetting phylosophy

I ordered following parts at Alle's R & D Performance and received them before the weekend.

160 MJ


35 and 38 PJ



I removed the air-cut valve, installed the MJ and the MAJ the PAS 3/8 or 55 and the 38 PJ.

Left the DXM on 6#

The bike started from the first kick, smooth power but a big bog when rolling-on (tried to eliminate it with the fuel screw) from in the low rpm's.

Whithout any logic thinking I swapped the 38 PJ for the 35 and installed the EMM needle on clip 5.

Starting was not as easy as before, still a little tickover when rolling too fast or wacking the throttle from in the low revs. Idle hangs for approx. 5 s after giving gas in neutral.

Guess the pilot circuit mihgt be a little lean (close the PAS ?)

On the other hand midrange and top are very satisfying. WATCH OUT FOR WHEELIES !!!!!

How cold I eliminate this tickover problem in low revs ?

Oh yes pump squirt is really small -0.5 s

Thanks Taffy, midrange and top rips :D:):D

that's a tough one to answer. you've dumped everything straight in and then made a major swap of needles! :D:)

i would drop the needle one clip and see how it goes. as far as the PC goes i would go back to the 38PJ and try that after.

i'm just shooting in the dark here. sorry!

it could come down to the fact that i said that a D serries was good for WR timing and an E series for YZ timing.


Hey Taff,

I am running the same: 38PJ, 162 MJ, EMN #2. I have my PAS at 1/4 turn out...

What do you think?

On decel (and NOT in neutral :) ) the backfiring is severe. I turned out my Kouba 1/2 turn and then the bike would stumble bad if the throttle was whacked open.

i'd open the PAS a little further kev. i know this sounds like leaner but it could be that both are needed. PAS and PJ up.

is it ok higher up?


I did not have a great area to test.

I have to put my license plate, headlight & tailight back on and take her on the road.

I DID search the forum and came up w/ that 1/4 turn open initial position.

At least I am not screwing w/ that carbon fibre airbox... :) That was a hassle to do carb work!

Hey Ynahg,

You did receive your Kouba...right??

Yes indeed Kevin, I received my Kouba.

By the way, forgot to thank you for that..so thanks for the Kouba :D


You suggest to go back to the 38 PJ, but with the PAS 55, but I think this was too rich, ran ok and a good idle with PS fully closed and started to run rough when opening 2 1/2 turns. Maybe put the 38PS and set The PAS to 60-65 ?, Or yust stay with PAS 55 and let the needle down a clip.

The more I'm understanding about jetting, the more this jetting compromise is getting complex. :)


without looking i think that 1/4 turn out on the PAS is #45 kev, so you had better start again!

i would drop the needle for the midrange pull test first. this has a side effect of very slightly leaning the PC. THEN do your PAS out to 3/8 turn. that is your second test.

the top end should ideally be done first. when i did jetting Qs i was going where the work was but you will have cut 90% of that out. the final testing in jetting Qs saw me doing three changes at once even though near the end it's ultra critical. but the fact is that by then i knew exactly what would happen if i did what to what.

good luck


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