Boring Out Throat of NT Carb

[Fabian]

Considering that my engine is equipped with a reed valve intake and a mildly modified standard muffler, and that my normal rpm zone is between 3,500 and 4,500, the standard 14mm carburettor and the 14mm Walbro style diaphragm carburettor are perfectly sized, going by your "ideal carburettor bore diameter" chart.

 

[Fabian]

The intake I replaced it with is 17mm inside diameter...

The 17mm intake tube will flow less than the number given because the airflow will be in a stalled state at the periphery of the non radiused bend in the pipe. It will however flow more than the standard aluminium 14mm intake tube.

I wouldn't mind betting that the maximum airflow of a stock standard 14mm NT carburettor with a straight shot reed valve intake would equal, if not exceed that of angle joined 17mm intake. tube and matching 17mm carburettor.