On my 05 Honda 400ex it spits out oil and leaks oil around the left side of the motor I'm guessing that means a new head gasket? Hopefully nothing worse, and when I bought it the previous owner said it needed rejetted so I bought the dynojet kit stage 1&2 it has a 426 big bore a hot cam and full yoshimura exhaust I put a 150 main jet in there and the aftermarket needle on the third notch, is the correct jetting.? It back fired before I jetted it and I rejetted it with the 150 and it still does it not as bad though, and when I'd start it it would act like it wanted to die but didn't and then I was riding it today and it kept blowing white smoke any guesses why? Any help would be great hopefully not about to break my bank...