The most effective way to heat a liquid-cooled is through the coolant IMO. Pad heaters have negligible effects in many conditions. Oil technology is such that viscosity problems can be overcome by purchasing good chemistry. A warm cylinder gets by the worst of the cold oil problems which involve the cylinder/piston contact. Added heat in the combustion chamber really enhances ignition at cold temps as well. Throw a quart or two of hot water into the cooling fins on a stubborn old ATV and you'll see the difference.
