TT-FCRMX39 Pilot Air Jet Removal

A way to big a hole to act as an air jet:bonk:

becuase it takes way more than 150 to do the job.

becuase it takes way more than 150 to do the job.

What about 150 PAJ with a smaller PJ or would it result in too small of a PJ ?

Is it just the idle to 1/8 throttle opening you're richening up with the PAJ removal or is there a significant overlap past 1/8 throttle ?

the same result can be achieved that way. once you get it sorted post up the final combo.

removing/larger paj leans the mixture. not richen.

idle to 1/8,yes.

the same result can be achieved that way. once you get it sorted post up the final combo.

removing/larger paj leans the mixture. not richen.

idle to 1/8,yes.

Yep sorry, I meant lean

I'm making some jetting changes since fitting a CW big bore.

Prior to the big bore I was running the following jetting at sea level, hot humid climate.

160 MJ

emR needle clip 2

42PJ

100 PAJ installed

3x3

Yosh RS2 uncorked

FS 1 turn (already indicating a bit rich)

I changed to 155 MJ when I fitted the BB kit

However it was way rich on the idle circuit cos I could close the FS without killing the motor.

Also felt rich at bigger throttle openings

I then removed the PAJ, refitted the 45 PJ, and put the emR needle back on clip 3.

This felt pretty good through all ranges above 1/8 throttle.

However Idle to 1/8 was way too lean even at 3 1/2 turns on the FS

I've ordered a 48 and 50 PJ to hopefully remedy this.

My only concern is if I'm risking being too lean at 1/8 to 1/4 throttle opening given the leaner root dia of the emR combined with any overlap from the PAJ removed ?

with the EMR needle and no paj you need a 48.

you already know its lean so i dont know what your "risking"? risking damage? no.

with the EMR needle and no paj you need a 48.

you already know its lean so i dont know what your "risking"? risking damage? no.

Yes, risking engine damage from being too lean at 1/8 to 1/4 .

Haven't read of any other members running emR without the PAJ, hence my concerns I might be going too lean.

Also assumed (perhaps wrongly) that the PAJ has some overlap to 1/8-1/4 throttle opening.

PAJ,Pilot jet and fuel screw have the exact same effect. idle to 1/8th throttle. 1/8 to 1/4 is straight diameter of the needle. yes there is some over lap but they should always be tuned 100% separately.

my suggestions more often than not take in consideration what jetting some one already has and working with it.

thus the removal of the pilot air jet instead of chasing super small pilot jets or different air jets.+

No worries, thx for the explanations

I'll be getting my 48pj next week and will update this thread with the results.

Tried a 48 PJ today.

Other jetting unchanged (emR clip 3, PAJ removed, 155 MJ)

Results not all that great.

Peak rpm ~2 turns and starts to drop down at 1 turn or 3 1/2 turns

Problem is it still backfires on decel, even at 3 turns on FS

Was no backfiring previously with PAJ installed and PJ 42, emR clip 2

However this was too rich even with FS at 1/2 turn out given the hot humid conditions here

Should I go for a bigger PAJ to use with the emR needle rather than removing the PAJ altogether ?

Alternatively, when I first got the carb the emN needle with PAJ removed was too rich with 45PJ. Since then I've bought a 42PJ so might try that combo as well.

Edited by bill1960

back fire on decel is normal. no back fire on decel is not normal. trying to tune it out will just leave you with a overly rich pilot circuit.

if peak rpm happened at 2 turns that is correct.

also if your bike is a euro or japan spec you need to block off the pair valve.

back fire on decel is normal. no back fire on decel is not normal. trying to tune it out will just leave you with a overly rich pilot circuit.

if peak rpm happened at 2 turns that is correct.

also if your bike is a euro or japan spec you need to block off the pair valve.

US spec, no PAIR

I understand there's a difference between backfiring and popping on decel, and that popping is normal, as is requiring choke to start when engine is cold.

As an experiment, I moved the clip pos from 3rd from top to 4th from top (richer)

This reduced the backfiring to normal popping on decel but unnecessarily richened the 1/4 to 3/4 throttle openings.

Can we deduce anything from that with regards to needle root dia ?

note: av riding conditions here are 85F and 80% humidity.

you must jet each circuit individually. moving the clip as you did proves exactly why.

there 2 needle root diamters between EMN and EMR. EMP and EMQ.

how ever you can simply install a 50 pilot or start gathering air jets and testing with different combos to you get the reaction want.

Current jetting is now

48PJ

FS 2turns

PAJ removed

emR clip 3

MJ152

MAJ200

3x3, RS2, 434 BB, Hotcams, 85F and 80% humidity, sea level

I think I'm fairly close with this jetting, except for the backfiring (not normal popping) on decel.

A 50PJ didnt improve it.

Experimenting with the needle on clip 4 reduced the backfiring to normal popping.

I think the problem is an off idle lean condition caused by the emR needle root dia combined with the PAJ removed.

Next step is to order an emQ needle

Also suspect the PAJ has more overlap to other circuits than the PJ.

Edited by bill1960

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now