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01 WR269 Help w/ Carb/Jetting

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howdy all,

after i installed my BB kit, ive rejetted per thumperfaq.com's method and the thing still seems really lean, i jet it down at my house in the LA basin, and it seems to run ok, but when i get up to where i ride in cal city/jawbone, its about 3K higher and much colder, normally that would call for leaning out the jetting (per the manual), but having tried going richer and leaner i simply cannot get the thing to run at all up here....yes ive tried spark, ignition coil, its a brand new kit and i know the compression is good, timing is good, it MUST be a fuel delivery issue

anyone have similar issues after big bore install? anyone ever have to go up to an FCR 41 or something after a big bore?

thanks

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What jets were you running before the BB...and what jets are you running now?

After installing the BB on my YZ269, I had it re-jetted on a dyno and it went from a #178 MJ to #160 MJ. The pilot jet stayed the same and the clip is in the 4th slot of the ('09)needle. My typical elevation is between 700-900' and the temp at the time of jetting was like 80*F.

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before the BB, i was running a 170 MJ, and 42 on the pilot

from there i tried going leaner, but it just ran the bike too lean and i was getting grey spark plugs, so ive gone gradually richer only stepping up jet sizes one at a time

and where i live i am at 48 pilot, 185 MJ, 5th clip needle which runs pretty well where i live 60s-80s about 200' elevation, but i ride at like 2K-4K in the 40s-50s (cal city if you're familiar) and it takes a serious hit in performance

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from there i tried going leaner, but it just ran the bike too lean and i was getting grey spark plugs,

With modern gasoline, you can't judge the color of the spark plug as a gauge anymore. You need to have a good feel or a dyno.

IMO, you're going wayyy rich. It's pretty hard to go so lean that this 4S will burn up. The bike will barely run before it burns up.

Also, the higher the elevation, the leaner you need to be. I'd go with the previous poster's jet recommendations and see what you feel. Don't read the plug but go by a butt dyno and sound. Good jetting sounds crisp and quickly goes thru the gears. Rich jetting sounds deep and laboring as it tries to rev.

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yeah not going by spark plug alone, but by how it runs, and anything leaner than a 45 pilot and it wont run....even at 45 i have to kick and kick and turn the idle screw way up as well as back the pilot screw way out ( per guide, anything more than 3 turns would warrant going richer)

thats the baffling part, it seems to need richer jetting for increase in elevation....

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