I do not know if the 45 has one . Most likely does. The 56 Sthil does. But you can check. You get to the muffler by removing about 3 screws. Once you see the muffler. You look for a small screw that holds the spark arrester down in the small slot. you just remove the screen with some needle nose pliers and clean it by heating it up then scraping it down with a wire brush until it's clean.
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I do not know if the 45 has one . Most likely does. The 56 Sthil does. But you can check. You get to the muffler by removing about 3 screws. Once you see the muffler. You look for a small screw that holds the spark arrester down in the small slot. you just remove the screen with some needle nose pliers and clean it by heating it up then scraping it down with a wire brush until it's clean.