Stihl 066 carb heat port.

  Back in 1991 I bought a new Stihl 066 Magnum chainsaw for the occasional big trees I encounter. The flat top cover had no provision (hole) for a compression release. I now need that feature because it's getting hard for me to pull start it. I purchased a new top cover #1122-080-1607 that will allow me to install a decompression valve, however I noticed this cover has no provision to fit the rotary shutter that controls whether or not hot air off the cylinder fins is allowed to come into the carburetor box. There is just an open port. My owners manual says this port needs to be closed if climate temperature is 70 degrees Fahrenheit or more. Looking through the Stihl parts book I don't see what was used to block off this port. How did the factory close off the port?

  The original cover had a rotary shutter that could be positioned to open or close the port. The new cover has no provisions for using the shutter. I'm just going to use some heat reflective tape to block the port on the new cover but I was wondering how they did it at the factory.