MalcolmR
CB750 New member
I have a persistent choke issue. Applying full choke from cold with the fast idle cam engaged (throttle plates slightly open) the engine dies. Spark plugs dry. Apparently the carbs have been split in the past. Work done so far - slow jets cleaned, slow jet circuit cleaned, new rubber caps on slow jet tower, new OEM float needles, new air cut off diaphragms springs and o rings, New choke cable,
Test performed used the master idle adjuster to mimic choke fast idle 2750rpm from cold, opened the choke gradually and rpm climbed. On fully deploying the choke the engine died.
Choke plates are solid and there is no adjuster screw on the fast idle actuating plate.
I understand the choke plates are designed to open under engine vacuum to allow air primarily into the air bleeds for the progression circuit (two ports behind the throttle plates part of the slow jet circuit) to feed an enriched mixture I to the cylinder. Is it possible the spring on the choke shaft has been wound too tight causing the choke plates to resist the engine vacuum?
Note once warm the engine runs well through all carburettor stages.
Test performed used the master idle adjuster to mimic choke fast idle 2750rpm from cold, opened the choke gradually and rpm climbed. On fully deploying the choke the engine died.
Choke plates are solid and there is no adjuster screw on the fast idle actuating plate.
I understand the choke plates are designed to open under engine vacuum to allow air primarily into the air bleeds for the progression circuit (two ports behind the throttle plates part of the slow jet circuit) to feed an enriched mixture I to the cylinder. Is it possible the spring on the choke shaft has been wound too tight causing the choke plates to resist the engine vacuum?
Note once warm the engine runs well through all carburettor stages.
