Vespa t5 polini 152 problems

Hi everyone. I have a mk1 t5, fitted with a polini 152 kit, 28mm pwk carb (new) and pm tuning pipe. It will hardly ever start and when it does run it runs at full revs (as if it has an air leak), it also has petrol in the gearbox oil. The problem is that i have changed all the oil seals, gaskets, blanked off the autolube and even replaced one of the casings, that had a small crack in it. But it still does it !! Can anyone help before it sends me mad [:P] . Thanks and ride safe.

Thank you for your reply. I have blanked off all the autolube holes and checked the carb. I have since had another close look inside the casings. The seals seem in good condition and fit well but the sealing ( rotary ) pad appears to be damaged and there is, what looks like, a hairline crack, in the main casing. The crank has a small area of damage too. I`m guessing that these could be my problem areas ?

If the carb is properly set up, your engine does clearly aspire air from somewhere, check the oil seal (flywheel side) and the intake manifold and carb. Of course you did not leave open holes removing the autolube, did you?