~ wrote:1) Warm up the engine to full operating temp.
2) Turn up your idle a few hundred RPM using the throttle stop screw (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. The whole procedure shouldn't take too long though.
Each time you change the screw setting 1/4 or 1/2 turn or so, wait about 5 seconds to let the idle speed normalize. It usually take the carb and engine a moment to react to the change.
3) Turn the fuel screw IN until the idle starts to drop and miss. The engine should die if you bottom out the screw. Your pilot jet is too big if it doesn't die when the screw is bottomed out--it should die before it gets that far in.
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.
5) 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 1-2 1/2 turns then your pilot jet is correct (the 1-2 1/2 turns applies to most carb types). 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 2 1/2 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.
To re-emphisize: If the idle never drops when you're turning the fuel screw in, you need a smaller pilot jet. If the idle never drops when you're turning the fuel screw out, you need a bigger pilot jet.
Typical fuel screw settings are in the 1 1/4 to 2 1/4 range.
6) Once you've got the fuel screw set, re-adjust your throttle stop screw (idle screw) to an appropriate idle speed.
And that's it! Your pilot circuit is now VERY close to ideal. From here you can experiment with how small adjustments affect low-end (i.e. small throttle openings) response and make adjustments for weather.
Eric Mac wrote:Will the setting of the fuel screw effect the color of the plug. I tore my bike down to lubricate all the suspension linkages and checked the valves. My plug looked pretty black, which would lead me to believe I need to lean it out a little. Either way, I will be following Agent Smiths directions for setting my fuel screw, but just wanted to hear if this will help the plug. Nice post Agent, even if you went through this on another post.
Yes if your rich anywhere it will change the color of the plug.
[email protected] wrote:Nice post AS,and that's the way to do it.
A lot of these settings depend on where you ride. My 450X for example, even fully opened airbox,red JD needle, full exhaust system,HotCams Stage 2, was happiest with a 162 main,45 pilot, and 1 and 3/4ths out. Lots of othe guys in different areas run 165-170 mains,and up to 48 pilots and they run great.
Regardless, AS described the right way to set that fuel screw. Doug
Once you get it perfect you'll be sooo amazed with your bike
~ wrote:1) Warm up the engine to full operating temp.
2) Turn up your idle a few hundred RPM using the throttle stop screw (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. The whole procedure shouldn't take too long though.
Each time you change the screw setting 1/4 or 1/2 turn or so, wait about 5 seconds to let the idle speed normalize. It usually take the carb and engine a moment to react to the change.
3) Turn the fuel screw IN until the idle starts to drop and miss. The engine should die if you bottom out the screw. Your pilot jet is too big if it doesn't die when the screw is bottomed out--it should die before it gets that far in.
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.
5) 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 1-2 1/2 turns then your pilot jet is correct (the 1-2 1/2 turns applies to most carb types). 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 2 1/2 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.
To re-emphisize: If the idle never drops when you're turning the fuel screw in, you need a smaller pilot jet. If the idle never drops when you're turning the fuel screw out, you need a bigger pilot jet.
Typical fuel screw settings are in the 1 1/4 to 2 1/4 range.
6) Once you've got the fuel screw set, re-adjust your throttle stop screw (idle screw) to an appropriate idle speed.
And that's it! Your pilot circuit is now VERY close to ideal. From here you can experiment with how small adjustments affect low-end (i.e. small throttle openings) response and make adjustments for weather.
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