400ex jetting issues

[laxman1306]

so ive got a 400ex .060 over piston 11.0 compression ratio open air box k&n filter stage 2 cam stock header 450r muffler stock muffler with no core...now i think its really rich at idle cause once its warm it runs great but when its cold it runs like crap. it pops bad, stalls and falls on its face...when its warm it runs like a top......so what would be the proper jetting for the mods i have?

oh and its still jetted for the 440 kit that was in it when i bought it....i believe its a 190 main stock pilot needle in middle, 3 turns out...also i have the idle speed screw all the way in and it wont idle higher it idles high enough to stay running

[CJM]

42 pilot, 2.5 turns OUT air/fuel screw and approx 165-170 main.

However .060 over? Are you sure? Generally they go stock 85mm, .020 (85.5mm), .040 (86mm), .080 (416mm), .120 (426cc) or I forget the measurement but 89mm is 440.

Generally they dont make a .60 (86.5mm) over unless its a weird company perhaps like namura or vertex. Wiseco, JE and CP dont make that size Im aware of.

Even if it is, Id jet for what I recommended. Should put you in ball park.

As for idling, you need to adjust the idle at the throttle on the bars a bit. Undo the idle screw (make sure its doing something by taking the carb cover off-it should push the throttle slightly). Adjust the throttle cable at the bars so you even if out between the bars and idle screw.

[laxman1306]

yep its kind of a odd ball piston its a namura 86.5mm

[CJM]

Then id say approx 165-170 main along with what else I said earlier.

[laxman1306]

needle position?

[laxman1306]

what about leak jet?

[DragonGunner]

Your jetting is probably ok for summer......if it runs bad during cold weather its becasue the air is denser.....change jetting OR you can put the lid on when its cold and it should run better,,with warmer weather you can take the lid back off

[laxman1306]

what i meant by the engine being cold is when i just start it ...it doesnt matter the temp outside

[CJM]

Leave the needle i the 3rd spot from the flatend, these carbs dont have a leak jet.

[riley1374]

I have almost the same mods except for open air box and full white bros exhaust. Needle moved one richer, 180 main and 42 pilot.