I am putting fuel filter on my sons 50cc as it does not have one. The quad has very small pipes 3mm ID, i need to put new 5mm ID pipe on to fit the fuel filter. The 5mm ID pipes fit the fuel tank cut off and the carb. Will this difference of 2mm on the fuel pipes make any difference? Will the carb need adjusted?

 

As long as the larger hose doesn't leak on the small barbs you should be good to go.

 

Ditto.
No adjustment needed.