Tia. I then decided to check the spark arrestor on my Stihl FS40 which is running fine (purchased in May 2015 also). Just waiting for my new catalog and I know they are expensive but was going to use the OEM dual ports from Bailey's. JavaScript is disabled. Mar 8, 2015. After using your machine for a total of 25 hours, it is time to clean your spark arrestor. QS 1141 140 8100. US $23.9 You will receive ONE spark arrestor THIS ONE IS FROM STIHL and is GENUINE PART NUMBER: 4140-140-6904 Fits Stihl models: FC 55. . Step 5. To locate the spark arrestor, locate the muffler on your Stihl chainsaw. I believe so. It can make you bankrupt in a single day. The design of the spark arrestor is to hold up the heat coming from the engine. The purpose of the damper is to regulate draft, help prevent heat loss and deter animal and other debris from entering the fireplace or chimney. My Stihl backpack blower was running at about 1/2 power, did the normal pm- plug, fuel filter, air filtersame issue. Does anyone sell the stainless screen material or is this just a hardware store type item? ,