Whats the equation for incomplete combustion of methanol

The basis for incomplete combustion is that instead of carbon dioxide being produced alongside water, carbon monoxide and carbon is produced instead, the carbon being released as soot. That handily sets the products up for the equation.

And combustion is simply a reaction between a fuel, in this case, methanol and oxygen.

The chemical formula for methanol is CH3OH. Simply write the reactants and products as a chemical equation and balance it, and you have the equation.