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--- tecnica:motori:keihin_cv_carburetor [2026/04/11 19:27] – [The Keihin CV carburetor] niccolo
+++ tecnica:motori:keihin_cv_carburetor [2026/04/14 18:26] (current) – removed niccolo
@@ Line 1: / Line 1: @@
-====== The Keihin CV carburetor ======
-  * Jet needle
-  * Main jet
-  * Needle jet
-  * Slow jet
-  * Pilot screw
-  * Float valve
-  * Choke valve
-  * Air cut off valve
-**NOTICE**: The terms **slow**, **idle**, and **pilot** are used more or less interchangeably in Honda manuals and Keihin carburetor documentation.
-{{.:keihin:keihin-side-view.jpg?180|}}
-{{.:keihin:keihin-float-chamber.jpg?180|}}
-{{.:keihin:keihin-vacuum-chamber.jpg?180|}}
-{{.:keihin:keihin-airbox-view.jpg?180|}}
-{{.:keihin:keihin-engine-view-bottom.jpg?180|}}
-{{.:keihin:keihin-engine-view-top.jpg?180|}}
-{{.:keihin:keihin-air-cut-off.jpg?180|}}
-{{.:keihin:keihin-jets.jpg?180|}}
-{{.:keihin:keihin-slide-diaphragm-needle.jpg?180|}}
-{{.:keihin:keihin-float-bowl.jpg?180|}}
-  * **Side view**
-    * Air intake from the airbox.
-    * Choke valve seat.
-    * Pilot screw seat.
-    * Duct for the high intake vacuum that acts on the //air cut-off valve// diaphragm.
-    * //Air cut-off valve//: air in (normally open).
-    * //Air cut-off valve//: air out.
-  * **Float chamber**
-    * Main jet
-    * Slow jet
-    * Starter jet (choke/enrichment jet)
-    * Float valve
-    * 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.
-    * Air intake for the choke.
-    * Small vent that connects the chambers above and below the diaphragm: it acts as a vacuum/pressure control and damping system.
-  * **Airbox view**
-    * Air intake for the pilot/idle and the //air cut-off valve// circuit.
-  * **Engine view, bottom**
-    * Primary pilot outlet port. This is the main idle fuel outlet, controlled by slow jet and pilot screw.
-    * Pilot progression ports. They provide staged extra fuel during throttle opening.
-  * **Engine view, top**
-    * 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.
-  * **Float bowl**
-    * Drain screw.
-    * Drain conduct.
-====== 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.
-===== Air cut off valve =====
-{{.:keihin:air-cut-off-valve_transient-enrichment-system.jpg?400|}}
-===== Web References =====
-  * **[[https://www.motorcycleproject.com/text/how_cv_carbs_work.html|How CV carburetors work]]** - {{:tecnica:motori:keihin:www.motorcycleproject.com-how-cv-carbs-work.pdf|Local PDF copy}}.
-  * **[[https://gadgetsfixitpage.com/article.php/the-keihin-cvk-40-carburetor|The Keihin CVK-40 Carburetor]]** - {{ :tecnica:motori:keihin:care-and-feeding-of-the-keihin-carb.pdf|Local PDF copy}}.
-  * **[[https://www.venturerider.org/forum/forums/topic/65604-what-is-the-name-and-purpose-of-this-carburetor-part/|"Coasting enrichment valve" or "air cut-off valve" or "transient enrichment valve"]]**