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athena 144 jetting

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Just thought I would share what jetting I arrived at after spending a bunch of time trying to get my 08 yz144 running right. I bought this bike used in the middle of winter. It has never ran right since Ive had it. That is my bad, I bought it in the winter. I just checked that it started and rolled without difficulty going into gears.  We wanted the bike because it had dubya hubs with black wheels and full hinson clutch and bunch of other aftermarket goodies my son wanted.  My son rides a yz125 which was my old bike. It is mostly stock except for a JD jetting kit. The JD jetting kit really smoothed out the hit on the 125 and I was happy with that.

Since I know it will come up, here are the things that were checked: vacuum test, pressure test, compression test, squish check, timing check, float height check. All those previous tests revealed problems that were corrected. The bike has Vforce reeds, stock pipe, stock silencer, and the standard Athena cylinder, head, and piston. I was about to give up getting this bike jetted right and looking into the lectron carb. I live in Illionois and it has been 68-80 degrees lately.  I tuned pilot circuit first, now it needs choke to fire up cold. I tuned by feel, judging performance after warmed up, doing rips up and down the street. Its probably not perfect, but it is way better than it was. What was strange to me, and messed me up with needle and needle clip choices was the fact that the pilot is so much smaller than factory 40 but I had to go richer on the main and needle.

30 pilot

air screw turned out 2 3/4

440 main

JD jetting RED needle 4th position

stock slide

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