not to start a great debate, I've used both yamabond and ultra copper with the exact same results, longterm leak free.
for those in a pinch, without a yamaha dealer handy or not open on a sunday, don't want to spend the $ on yamabond, ect. ect. ultra copper works
Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker:
OEM specified for high operating temperatures common in 4-cylinder, turbocharged or high-performance engines. The most advanced, high temp RTV silicone gasket available. Sensor-safe, low odor, noncorrosive. Superior adhesion. Three times more oil resistant than conventional silicones; eight times more flexible than cut gaskets. Temperature range -65°F to 700°F (-54°C to 371°C) intermittent;
resists auto and shop fluids and vibration
recommended uses:
Exhaust manifolds/headers, Exhaust header flanges, slip fit exhaust pipes, muffler end caps, valve covers, oil pans, timing covers, water pumps, thermostat housings,
intake manifold end seals
http://www.permatex.com/products-2/...-temperature-rtv-silicone-gasket-maker-detail
or....
Permatex® MotoSeal® 1 Ultimate Gasket Maker Grey
For two and four cycle engines. Solvent-based bond fully seals within 20 minutes. Forms a tough flexible bond that is highly effective on irregular and uneven joint surfaces. Resists gasoline and other damaging fluids. Withstands temperatures 350°F (177°C) continuous, 400°F (204°C) intermittent.