Yamaha YFM660FS Grizzly 4x4 Supplementary Service Manual page 185

CLEANING THE SPARK ARRESTER
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Tap the tailpipe lightly with a soft-face ham-
mer or suitable tool, then use a wire brush to
remove any carbon deposits from the spark
arrester portion of the tailpipe and the inner
contact surfaces of the muffler.
Insert the tailpipe 2 into the muffler and
G
align the bolt holes.
Insert the bolt 1 and tighten it.
G
G
Start the engine and rev it up approximately
twenty times while momentarily creating
exhaust system back pressure by blocking
the end of the muffler with a shop towel.
G
Stop the engine and allow the exhaust pipe
to cool.
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