My MS 430 C has been going great for 18 months but lately the lever
which shuts off the engine has ceased to function.

I slide it up for STOP and it jumps back to RUN.

To stop the engine I put it to foll choke.

Looking inside whenever cleaning the air filter I see nothing unusual,
but how does one know what it all should look like? Is there a source
of drawings / photos of this area? Or, is there a reason this problem
might arise?

Thanks
Phil