Many Yamaha motors use metal gaskets between
major components, such as cylinder heads and the
crankcase, as well as the crankcase-to-upper-casing
exhaust guide. Most of these metal gaskets use
factory-applied surface coatings and raised ribs to
seal between components. There is no need to apply
additional sealant when reassembling components.
In fact, when additional sealant is applied, it typically
winds up in the oil pan, eventually finding its way
to the oil pick up screen and restricting oil flow. We
all know what happens after the screen becomes
clogged.
If in doubt about where to use sealants when
assembling components, always refer to the
applicable Service Manual. When sealants are
required at specific locations, there will be a tube
icon with the sealant number as shown in the
adjacent F150 cylinder head assembly drawing.
Notice there is no sealant specified for the cylinder
head gasket.
When assembling components that use metal
gaskets, it is important that neither gasket surfaces
nor component mating surfaces have scratches. Also, pay particular
attention to sealing ribs that may have been crushed
or dinged due to improper handling