I have a 1977 Puch newport. It came with nasty 20 year old expired 2-stroke gas in it that had been sitting since probally 1977. Ive been working real hard on flushing the gas tank but I just cant seem to get anywhere. Ive used methods like soaking the tank in vinegar, but recently ive been flushing the tank through with paint thinner, blowing compressed air through it and sucking things out with a vacuum cleaner. And after all of that work im still getting nowhere. Im hesitant to use harder solutions because the moped has 400 on the spedo, and a beautiful apple finish on it, which I would not want to ruin at all. But after 15+ flushes theres still bits and peices of rusty compound. Need some insight on how to do this without ruining my carb and fuel filter.