400ex Pilot Jet Installation/Exchange (written by Zingnut, editted by Lrd Mx400ex)
Purpose: To either correctly jet your bike for a new engine modification or to put in a 42 pilot jet to cure winter starting troubles.
1. Turn your gas valve to off.
2. Start the quad and let it idle till it dies from lack of gas.
3. Remove the rear seat and rear fender.
4. Remove the two 5mm allen head bolts from the front plastic.
5. Remove the four 10mm bolts that are under the front fender.
6. Take off gas cap.
7. Remove the plastic gas tank cover.
8. Pull the front fender forward and out of the way of the gas tank.
9. Remove the two 10mm gas tank bolts and two rubber straps that are one either side of the gas tank.
10. Remove the gas line from the gas valve.
11. Remove the gas tank.
12. Remove the 10mm bolt on the air filter box and then loosen the screw clamp on the carb and airboot.
13. Remove the clear catch container from the clutch side of black air filter tube.
14. Remove the push lock from the clear plastic intake tube.
15. Pull off the air filter and clear intake tube.
16. Loosen the screw clamp on the motor side of the carb.
17. Remove the carb.
18. Remove the four phillips head screws from the bottom of the carb (see Figure #1).
19. Remove the plastic ring from the main jets (see Figure #2).
20. Gently remove the Pilot Jet from the carb (see
21. Gently screw in the new #42 Pilot Jet. DO NOT OVER TIGHTEN IT!
22. Put your ATV back together using these directions in reverse.