OK, well your latest comment confuses me. You mention that the throttle drifts back if the throttle cable is connected. But, if you disconnect the cable and control the throttle at the engine, it doesn’t drift? Kind of doesn’t make sense, but I’m sure I am confusing what you are saying. Don’t know how that little accessory works that Bill mentioned, but it seems like a simple solution if it works.
Keep in mind that there is some “slop” in the engine throttle linkage, which makes some throttle drift unavoidable. There is natural spring tension in the engine’s throttle linkage as well, that will always favor lower speeds. The carb throttle shaft is spring loaded, along with the economizer linkage, both these parts will favor lower speeds. All that being said, it is important to ensure the throttle cam pick up is set properly, along with the economizer linkage (I’m pretty sure this engine has this feature, perhaps not though.. Look for a long thin horizontal rod that runs from the carb butterfly back to the vertical throttle rod on the port/left side of the engine under the flywheel). The rotational forces on the coils from the flywheel magnets will favor a slower/retarded setting as well. Again, please be sure the flywheel magnets are not rubbing on the flywheel. This can usually be determined fairly easily. Remove the spark plugs, disconnect the battery, disconnect the remote throttle cable. Now, set the throttle to a mid point setting where it will stay on its own. Now, rotate the flywheel in a clockwise direction. Does the mag plate seem to drag on the flywheel magnets and move with it towards idle position? If so, it is a good idea to pull the flywheel (OMC puller needed), and look at the coil laminations to see if they have been rubbing on the magnets. Don’t forget to retorque the flywheel nut properly afterwards. Improper torque could cause the flywheel key to shear (losss of spark) and damage to the flywheel/crank tapers. Overtorquing could cause the flywheel tapers to spread so the flywheel will never lock in place and continue to shear keys.
