jetting quad?

[jeremy_283]

kk i know i have had a lot of carb adjusting questions but heres another. To figure out if the pilot screw is adjusted right can u put in a new spark plug and see if it is golden-brown after letting it idle for a while?

[GPracer2500]

The best way to find the proper setting for the pilot screw (aka fuel screw) is the following. This method can also indicate if your pilot jet is too big or too small.

1) Warm up the engine to full operating temp.

2) Turn up your idle a few hundred RPM (basically you want a fast idle). This will make it easier to hear small changes in RPM. Watch for overheating--pointing a big shop fan at your engine will help it from getting too hot during the fast idling.

3) Turn the fuel screw IN until the idle starts to drop and miss.

4) Then begin turning the fuel screw OUT. The idle should peak and become smooth. Keep going and look for the idle to begin to drop/miss again.

The goal is to find the setting that provides the highest and smoothest idle. If it's unclear exactly were that point is then set to the midpoint between step #3 and step #4. For example, if the idle starts to drop at 1 turn out and starts to drop at 2 1/2 turns out then 1 3/4 of a turn out should be the correct setting.

If the peak/smoothest RPM is reached somewhere between 1-3 turns then your pilot jet is correct. If you end up less than 1 turn out then your pilot jet is too big and you need a smaller one. If you end up more than three turns out or the fuel screw seems to make little difference as you continue turning it out than you need to go up (bigger) on your pilot jet.

Typical fuel screw settings are in the 1 1/2 to 2 1/2 range.

It is quite difficult to adjust the fuel screw on a stock 400EX carb while the bike is running without a 90 degree screwdriver. I bit the bullet and bought this one from MotionPro. It works well but I'm sure there are others available.

http://www.motionpro.com/images/groups/144.jpg