QuestionI AM REPAIRING MODEL 917.272461 FOR MY BROTHER. THE MOTOR SURGES AND THE THROTTLE SPEED CAN ONLY BE CONTROLLED BY THE CHOKE.I TRIED ADJUSTING THE GOVERNOR, THROTTLE CABLE AND CHOKE CABLE.I REMOVED THE CARBURETOR AND CLEANED ALL VISIBLE PARTS.INSIDE THE FLOAT BOWL I DID FIND METAL LIKE DEBRIS WHICH I REMOVED.THE FLOAT DID SEEM TO OPERATE.THE GOVERNOR CONTROL AND BRACKET CONTROL SEEM TO OPERATE. NEW PLUG, GAS AND OIL. ALL THIS AND STILL THE SAME SYMPTOMS. CAN YOU OFFER ANY HELP. THANKS VINCE
AnswerVince
Engine hunting and surging at true idle is caused by a fuel delivery problem or an air leak. True idle is the carburetor setting when the throttle plate linkage is against the idle speed adjusting screw after idle mixture adjustment. Because the throttle plate is held stationary during true idle, hunting and surging must be caused by an improper air-fuel mixture related to an air leak or an obstruction in the idle circuit. At true idle, the governor spring applies no force on the throttle plate and has no effect on the idle characteristics of the engine.
Hunting and Surging at Governed Idle
An engine hunting and surging only at governed idle and equipped with an idle mixture adjustment has a governor system or carburetor problem. The idle mixture must be adjusted correctly. Hold the throttle plate linkage against the idle speed adjusting screw and increase the idle speed to the specified governed idle speed. If the engine operates without hunting or surging, the problem is the governed idle spring or linkage. If the engine continues to hunt and surge, the problem is in the carburetor. After testing, return the engine to the correct idle speed.
Hunting and Surging at Top No Load Speed
Troubleshoot hunting and surging at top no-load speed using the same sequential steps used to isolate a governor system or carburetor problem during true idle and governed idle. Once the idle mixture is adjusted and the engine idles smoothly, increase the engine speed using the idle speed adjusting screw. Hold the throttle plate linkage against the idle speed adjusting screw until the engine reaches the specified top no-load speed. Without any appreciable load, fuel is provided by the idle circuit. If the engine continues to hunt and surge, the carburetor is the probable cause. In this test condition, the governor system has no effect on engine speed. The idle speed adjusting screw control the throttle plate position, which affects engine speed. If the engine operates properly when controlled by the idle speed adjusting screw but hunts and surges when controlled by the governor spring, the governor system is suspect. Check the governor linkage for resistance and binding, and replace the governed idle spring and the main governor spring.
Hunting and Surging Under Load
Hunting and surging under load usually indicates a carburetor or fuel delivery system problem rather than a governor system problem. Fuel fed under load is primarily fed through the main jet and emulsion tube. Most loads are constant enough to maintain the rpm of the engine. The governor system has very little additional effect on the performance of an engine under load except for applications with sizable varying loads such as a minibike go kart or generator.
