air fuel mix screw [Archive] - ATV Riders Forum

Dannys400ex

01-23-2005, 10:51 AM

i just removed my choke from my carb, and need to know where to set the mixture screw. elev. around 800- 1200 ft. im in NC. 440 kit, k&n filter with outerwear and no lid. i have the outerwear box cover. xr400 cam. ant ideas where i should start? big gun full system.

thanks

Dannys400ex

01-23-2005, 10:55 AM

just looked up ele. im at 1203 ft.

cals400ex

01-23-2005, 01:35 PM

i would put in a larger pilot jet first. with a larger pilot jet in i usually start around 2.5 turns out from lightly seated

Dannys400ex

01-23-2005, 01:38 PM

sorry i didnt say that in the first post. it already has a 42 pilot in it.
and thats where i started it was a t 2.5. just wanted to make sure. do you think i will have to adjust the mix more?

ssanddemon

01-23-2005, 09:45 PM

Rule of thumb on idle air screw adjustment is this: Raise idle speed with the idle speed adjustment screw about 200 rpm or so above normal. Turn the air screw in or out to obtain the highest rpm (operating range of the screw is usually 0 to 3 turns out from seated). Use the idle speed screw to lower idle speed back to the lowest consistent rpm, and your'e done! FYI, the same pilot jet works in a large range of engines. If yours is stock, it's probably still right even with the engine mods.