Murray G20300000 3hp Single Stage Snowblower - Spring-loaded butterfly carb lever

[Martin Collins]

Hi All,

I recently acquired an old Murray 3hp single stage snowblower (Model No: G20300000) and I decided to tear down the carb to give it a good clean in preparation for the winter. Upon putting everything back together and starting the engine I realized that the engine was running way too fast. Upon further investigation, I discovered a white plastic lever that is connected to the (spring loaded butterfly valve located on the) top of the carb by a small thin connecting rod - see plasticlever.jpg attached.

By adjusting this lever, I can control the RPM's of the engine. Now for the life of me I cannot figure out if or how the plastic lever is meant to be adjusted or if it is meant to lean against anything. The lever is actually hidden by the engine top cover (see below pic) so that is why I did not notice it when I was removing the carb for cleaning - see engine cover.jpg attached.

There is nothing inside this top cover for the lever to attach to or rest against nor is there any other parts of the mechanics of the snowblower that I can see it that the lever connects to. Furthermore, there are no holes on the plastic level itself other than the point where the small thin connecting rod attaches to the top of the carb.

Does anyone have any idea what I am supposed to do with that white plastic lever?

Leaving it as it is is no good because the resting position of the level results in the butterfly valve being open which means that the engine is running at maximum RPM's. At this point I am tempted to just ziptie the lever to hold it in a certain position at a point where the engine RPM's are comfortable but this seems like such an insane kluge to me and is driving me nuts how I can't figure out what on earth I am supposed to do with that white plastic lever.

Any help would be most appreciated!

Thanks,
Martin

 

[artemjemmy]

That plastic piece is an air vane governor. It acts like a sail, creating a force in response to air flow created by the flywheels air vanes. This force acts against the throttle spring (to the left of the air vane) to try and close the carburetor butterfly. So when the engine is running too slow, the air vane is not creating enough force and the throttle spring pulls the carb butterfly open, in an attempt to increase engine speed until the air vane does produce enough force, overcoming the force of the spring, and the two forces finally equalize and the throttle butterfly settles at a nice position to maintain a desired engine RPM for any load on the engine. Negative feedback! It is perfectly normal for the butterfly to be open right now, because there is no air flow, so the air vane is doing nothing and the throttle spring is opening the butterfly. However, if something is sticking, the air vane will not be able to move and will cause your problem where the butterfly is stuck open. Make sure that the throttle shaft and the air vane can move smoothly, without binding or sticking. You also need to have that blower shroud on because air will not be properly deflected into the air vane and it will run too fast without it.