Yes, it varies, not so much by engine size, but by:
1. Road speed. 120kph vs 100 makes a huge difference
2. Engine RPM. 4000 vs 3000 RPM makes a huge difference, as much as 20% at the same road speed! Hence the advantage of a 5-speed

My datto gets 350km per tank if speeds arer kept below 80 but only gets 300 as soon as its doing 100kmph trips. my carb is rich though im running a a15 with a 200b carb.

i am getting at least 65 km per 5.5 liter. usually 70 to 75. A12A b310, 4 speed box.

Hey guys just wondering what kinda fuel mileage all your a series get...
I'm constantly getting 142miles out of a full tank of shell v power on a heavily worked twin webber a14..

That's driving to And from work stopping and starting..

So fuel mileage around town