Here are some napkin calculations:
50 MPG/ 50 miles per hour. One gallon per hour consumption.
A one quart jar (1/4 of a gallon) would drain in 15 minutes (1/4 of an hour) if that were your fuel tank.
If your bike got 25 mpg @50mph, you'd use a quart in 7.5 minutes.
12.5 mpg : a quart in 3.75 minutes
Attach hose on petcock and aim it at a one quart jar. Turn on petcock, time how fast is fills. If it takes longer than 4 minutes, you have a restriction issue.
How bad is your gas mileage/ fuel consumption?
About larger hoses:
A bigger hose does allow higher liquid flow rates. However, the flow rate is limited by the smallest restriction in the flow path. Using larger hoses and smaller I.D. size fittings negates any benefit from the larger hoses. Unless, of course you are talking very long hoses. But, that is another fluid dynamics problem.
By the way, I used a pink napkin with floral embossed pattern. Some might say it was rose colored.
Cheers,
