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09 kx269f jetting in cold weather

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hello i have a 2009 kx250f with the cylinder works 269 big bore and pro circuit ti4r exhause i ride around 500-1500 elevation and its be in the 60's over winter.

mysetup

178

ncys clip 3

45 pilot

im not sure if im even in the ballpark and recoomendations? i perfected jetting my 2 strokes just as i moved over too 4 strokes but im just getting into this bike so i dont know where to start

Edited by Dasquriel

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pilot jet seems a tad bit rich.. How ever rule of thumb cold weather increases air density thus allowing the use of a richer fuel setting.. So 178 maybe lean in the colder weather.. I would say though 178 in warm weather is on the still fat side so 178 might be perfect as it is.. 42 pilot is the norm and a 45 would be slightly rich so in colder weather the 45 might work but I would say it's probably still rich also..

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Right now in SC roughly 50 degrees. I'm running:

175 main

ncys 3rd clip

42 pilot

2 1/2 on the air screw

Right now it's dead on but I'm going to toss in a 40 pilot here soon and see what happens.

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^ thats what i run but i wouldnt go down to a 40 in this weather you should go up to a 45 now

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Well, shit I just realized that you're running a BB.. Sorry then I was quoting running the stock 249cc setup.. So I maybe wrong.. How ever in all reality dropping in temperature allows the air to be denser so regardless you will need to increase the fuel mixture if you were spot on in the summer months..

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not that it helps but I 've got an 09 with a slightly higher compression piston have to run 50/50 race pump gas. Spoke with a 09 kxf 250 racing professional mechanic about cold weather jetting. for temps in the 20's and 30's at sea level. He said to run 45 pilot, 185 main needle in the middle slot. rode it last week at about 35f seem to work well. my take on these things is, better off rich than blown up. Start fat and work it back from there!!

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^ i dont ride much under 40f but i will put a 45 pilot and 182 main, with a 269bb you dont change jetting much its very close

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