you need to use addPedClothes in the spawn function. for example
function spawn(player)
repeat until spawnPlayer( player, -1259.3856201172, 163.54290771484, 14.1484375)
addPedClothes ( player, "moto", "moto", 16 ) -- this would be a blue helmet
fadeCamera(player, true)
setCameraTarget(player, player)
end