Pilot Jet

[FoxMxRiders]

My 400 is stock for now

I run a dynojet kit : 3.5turn on the pilot screw,needle on the 3groove and 142 main jet

My quad run good

But If I change my pilot jet to a 42 and remove my choke,how many turn on the pilot screw that I will need to run good?

[cals400ex]

with the 42 in place, i would start around 2.25-2.5 turns out.

[bwamos]

The trick is to start at 2 turns.
Start the engine.. idle it.
Slowly screw the idle screw out.
You will hear the engine speed up a little.
Keep going until it stops increasing rpms - this is the lean threshhold (percfect combustion.. but HOT).
Then screw it back in a 1/4 turn to cool it back down..
This is the perfect idle screw setting.

If it doesnt speed up.. restart at 1.5 turns. repeat as necessary.

[cals400ex]

Originally posted by bwamos
The trick is to start at 2 turns.
Start the engine.. idle it.
Slowly screw the idle screw out.
You will hear the engine speed up a little.
Keep going until it stops increasing rpms - this is the lean threshhold (percfect combustion.. but HOT).
Then screw it back in a 1/4 turn to cool it back down..
This is the perfect idle screw setting.

If it doesnt speed up.. restart at 1.5 turns. repeat as necessary.


you are correct with saying that turning the pilot screw by the fastest idle is best. however, turning it out makes it richer, not leaner. i have tried this and didn't notice much idle fluctuation. you are supposed to use a tach when doing this. i didn't have one so i didn't. also, i usually jet this pilot screw a hair rich because we all know the air cooled 400ex's need all the help they can get with trying to stay cool. the pilot screw is a fine tune adjustment for the pilot jet. these mainly control fuel flow at idle.

[FoxMxRiders]

When I don't have the dynojet kit installed,I try to adjust the pilot screw and never hear the motor speed up,I don't have a tach.Then when I installed the Dynojet kit,I follow the instruction and turn it a 3.5turn and run good

Then maybe 2 - 2.25 turn ?

[cals400ex]

with the 42 in place, i have a feeling you will end up around 2-2.5 turns out. if you want to go a little leaner you probably could though.

[FoxMxRiders]

thanks

do you have a tips for a stripped screw on my carburator bowl?

I have a manual impact wrench and Mastercraft Drill out tool

[cals400ex]

a lot of these screws i get a screwdriver and tap the screwdrive in a bit with a hammer. the screwdriver tends to bite harder in the screw and they come out easier. not sure what else to tell you.

[250rAL]

Just use a small Visegrip and clamp it on the head of the screw. Carb screws always have large heads where this trick will work.