Continuing my ongoing saga to properly fuel the FMF exhaust system (Megabomb+Power Core 4) has led me to heresy and the committing of blasphemous acts - I put back in the stock KLX250S needle. This is the way I've chosen to attempt to lean the low and mid RPM range to a more proper AFR with the DJ144 main jet.. The other option I considered was using the stock slide spring with the DJ needle - I like the slide performance with the DJ spring, I just don't like the overly "fat" (rich) low and mid of the DJ needle.. Look at my latest chart on my FMF dyno tuning thread to see how fat the AFR went with the DJ needle..

Data for new members and visitors: 2012 KLX250S, MCM cam retime, Uni airfilter, backfire screen removed, de-smogged, Megabomb+PC4, airbox lid off, DJ2152 kit with DJ144 main jet, #40 Pilot jet, Stock Needle, 700 ft ASL...

Test rode for about 20 min. It runs just fine. Low RPM throttle response is definitely improved- this means it responds stronger to throttle jabs below about 5k RPM.. Power levels in the mid to upper @ WOT - all I can say right now is "inconclusive".

I'm bout to go riding with my daughter for a while.. Perhaps I'll have a chance to fine tune my analysis..

 

With just the FMF Q4, is the DJ needle, DJ140 main, and #38 pilot still the way to go?

 

Yes, Michaelb2.. The DJ2152 kit + Jet assortment (DJ140, DJ138, DJ136) and a #38 Pilot will let you choose an AFR for your pilot system - all of this is for Near Sea Level, and lidless with aftermarket silencer (slipon)..

IMHO, if your summer temps are much above 85F, (SAE standard is 77F, so that is what my charts are corrected to..), I'd start with 138/3N..

 

Where can I source said assortment and pilot? I've been looking around. I can find jets, but they're not always for the CVK34 carb, which I'm assuming is what I have based on the manual. Do you have a favorite vendor?

 

You call DynoJet and order the jets. Get the kit anywhere online or from your local cycle shop,. Order the pilot jet from a Kawasaki shop - the part numbers are in here on one of the stickies..

 

Mo ridin dun.. It seems to be a good setup.. I'd say "this is it" except I've felt this way before - then came the Dyno results - Turns out, I had picked a bad day to quit sniffing glue..

Soow den, ah dino sesson b kumin..

 

u fokin wot m8?

 

Why not lean it as you want it with a 38pj and keep the DJ needle?

 

Hey Richard, the pilot system doesn't work like that. It produces usable/tunable AFR only under high vacuum operations - closed throttle decel, idle, and certain conditions of small throttle openings with high engine RPM (such as cruising at 3-4K RPM @ 1/8th throttle in, say, second gear).. I have my #40 Pilot set toward lean right now..

I needed, at least, several entire points of AFR change in the middle - 4k to 6.5k rpms..

 

Hey guys, remember this thread is VERY old and I was still deep into experimentation with pilot jets, main jets, slide springs, needles and clip settings...

So everything in here has been superseded with better setups. There is NOTHING in here that is helpful to the membership and I should probably DELETE this thread to keep eager minds from going off "half cocked"..

However, in the end, data from this experiment was not lost to me - it culminated into the knowledge that a .060 shimmed stock needle CAN be used to good effect in a few particular mod combos.