Waste of time. At the least you'd have to open out the inlet port in the head. If the carb is a slip-on type, you will need to machine a new connecting manifold. If bolt-on, chances are that bolt spacing will not suit, so you will need to machine some sort of adaptor plate.
As for performance increase - if done properly, you could expect a reasonable increase in HP, until the poor old underperforming GN motor gave up under the strain.
Do you realise how many holes there could be if people would just take the time to take the dirt out of them?
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