tecnica:motori:keihin_cv_carburetor
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Table of Contents
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.
- 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
Web References
tecnica/motori/keihin_cv_carburetor.1775935685.txt.gz · Last modified: by niccolo