QuestionHI, I HAVE A YAMAHA DT400, TWO STROKE. RUNS REAL GOOD. AFTER IT'S REALLY WARMED UP, IT STARTS IDELING VERY ERRATIC, JUST LIKE IT'S RUNNING OUT OF GAS, THROTTLE GOES UP AND DOWN AT IDEL. WHAT SHOULD I LOOK AT, HAVE CLEANED CARB AND PETCOCK, ONE OF THE OTHER EXPERTS TOLD ME TO LOOK AT AN INTAKE AIR LEAK, WHAT EXACTLY WOULD THAT BE. AND DO YOU HAVE ANY MORE ADVISE, THANKS CHAD
AnswerChad, not much of a 4 stroke Honda question, but I'll take a shot.
Erratic idle conditions can come from any one or a combination of the following:
Restricted fuel passages/air passages in the carb.
Restricted fuel passage in the petcock.
Unvented fuel cap
Bad crankshaft bearings, allowing air to be drawn in past the crank seal on the ignition side... or just bad seals.
Bad transmission side crankseal sucking oil into the motor.
Air leaks at the intake manifold where it mounts to the cylinder or carburetor... cracks in the rubber or bad gaskets.
Incorrect fuel level setting in the float bowl (float level setting).
Defective choke circuit parts.
Incorrect ignition timing.
Bad spark plug/plug cap or coil... weak spark from igntion.
Sticking or damaged piston rings.... low compression.
Carbon blocking the exhaust port or muffler.
Incorrect oil mixture (either premix or injection system)
http://www.powersportspro.com/partsfish/login.asp
Log in and check the microfiche illustrations to get a better idea of the parts and how they go together.
Better yet, find a factory repair manual online...
Bill Silver
