Motorcycle Repair: Oil in air filter, stud holes, head gasket

Question
Hi I was just wondering, I filled my oil up last week, takes a full 1ltr and I put in approx 800ml as there was no oil on the dipstick! looked yesterday to find my air filter is swimming with oil! Just wondering why this happened? People mention that there are breather pipes, where would they be and the only pipe I have seen at first look is one that connects from oil tank (well the part I put oil into that said oil on dipstick) directly to the air filter chamber! Wouldn't have though I overfilled it but am not sure, any help would be much appreciated! Also another thing, I took cylinder head off to get exhaust stud holes helicoiled and since bike has been a lot noisier and vibrates more, it was around the same time I filled with oil and the pro that did helicoils said head gasket will be fine and wouldn't mean bike would be louder etc! Any ideas? Thanks for your help in advance! Not sure if it makes any difference but its a sukida patriot sk125-5 125cc

Answer
Most of the scooters from china have 4 styles of engines. Its possible that its overfilled or if there are a lot of miles on it,its possible that it has alot of blowby which also can pump excess oil into the air box. Try draining the oil again and put in the correct amount,make sure bike in on center stand and level.this should give you the best results.