Intake burnt, oil gasket leak.

[Moggy]

There are many reasons which contribute to the German defeat during the battle. 1 contribution was in fact German radar which was far in advance of the British chain home system. This led in part to the Germans simply believing the British system was ineffective. Another factor which is often overlooked was the British control of German intelligence gathering, All of the German spies operating in Britain had been captured by or during 1940 and some were double agents. 1 particular spy (Garbo?) fed false information about British aircraft production, telling the German high command that Britain was producing 200 fighters a month...the same as Germany. The figure of course was much higher (about 450 fighters a month give or take), so the Germans naturally thought to win all they had to do was keep pace with the ficticious production figures.
It's perfectly understandable to see why Goering thought (quite wrongly) the RAF was on it's knees.
There's no simple reason why the Germans lost the battle, it really is a huge combination of facts, circumstances, opinions, personnel, innovation and even double bluffs.