Differences

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--- tecnica:motori:keihin_cv_carburetor [2026/04/10 21:29] – [The Keihin CV carburetor] niccolo
+++ tecnica:motori:keihin_cv_carburetor [2026/04/12 10:35] (current) – niccolo
@@ Line 1: / Line 1: @@
 ====== The Keihin CV carburetor ======
+{{ .:keihin:honda-ntv650-keihin-carburetor-code.jpg?direct&200|}}
+Here some details about the carburetors mounted on the Honda NTV 650 Revere. They are two Keihin carburetors marked as **G4AACDt**. They are constant velocity (CV) carburetors, that uses engine vacuum to operate a diaphragm-controlled slide, rather than a direct cable connection.
+===== Nomenclature =====
   * Jet needle
@@ Line 31: / Line 37: @@
     * Pilot screw seat.
     * Duct for the high intake vacuum that acts on the //air cut-off valve// diaphragm.
-    * //Air cut-off valve//: air in.
+    * //Air cut-off valve//: air in (normally open).
     * //Air cut-off valve//: air out.
   * **Float chamber**
@@ Line 40: / Line 46: @@
     * Breath hole
   * **Vacuum chamber**
+    * Air intake from the airbox.
+    * Starter (choke enrichment) air supply passage.
     * Air intake for the //air cut-off valve//: normally open. It closes on deceleration (high rpm + throttle closed).
     * Air intake for the slow jet.
@@ Line 50: / Line 58: @@
     * Pilot progression ports. They provide staged extra fuel during throttle opening.
   * **Engine view, top**
-    * Vacuum conduct that operates the //air cut-off valve//.
+    * Starter (enricher) outlet port and vacuum pickup port that operates the //air cut-off valve//.
   * **Slide, diaphragm, needle**
     * Slide lift holes: vacuum bleed holes that control how quickly pressure changes reach the above diaphragm chamber.
@@ Line 57: / Line 65: @@
     * Drain conduct.
-===== Air cut off valve =====
+===== The pilot screw =====
+The Pilot screw is on the engine side of the carb, located after the pilot jet, it is a fuel screw.
+  * Turning it IN (tightening clockwise) reduces fuel flow, leaner mixture
+    * Effects:
+      * Harder cold start.
+      * Lower idle speed.
+      * Possible hesitation off idle.
+      * Lean deceleration popping.
+  * Turning it OUT (loosening counterclockwise) increases fuel flow, richer mixture
+    * Effects:
+      * Smoother idle.
+      * Better throttle pickup.
+      * Easier starting.
+      * Reduced decel popping.
+===== The air cut off valve =====
 {{.:keihin:air-cut-off-valve_transient-enrichment-system.jpg?400|}}