Topic: RPM Range for Best MPG

[Stev-o]

Sean, Mooshie has done in the 50 MPG range with Dash, IIRC? Of course, it should be mentioned that Dash is equipped with pods.

And she is much lighter than most of us!

[754]

I would get 50 to 55 on my wore out 836 with Webers when I rode it Utah year's ago.
 I don't think a 750 is real good till,  at least over 40 mpg

[seanbarney41]

seems like Weber carbs somehow add a good bit of mpg

[scottly]

Cruising at 65-70 MPH, the throttle valves are barely cracked open, and the pilot jets are still in play. Whack the throttle open, however, and the mileage drops like a rock.

[Maraakate]

On my 77 CB550K which is mostly stock except for some 1990's era aftermarket 4-into-2 (unknown brand) exhaust around 4000-5000 RPM cruising mostly around 55-65MPH in 5th gear I get about 45-50MPG on average.  However, this is only if I use ethanol-free fuel.  I noticed when I use 10% ethanol I get about 35-42MPG on average.

[American Locomotive]

seems like Weber carbs somehow add a good bit of mpg

I think it's because the Weber carbs are not slide carbs. On slide carbs, your air fuel ratio is all over the place because the velocity through the venturi is constantly changing. Whack the throttle wide at a low enough RPM and your engine will just about cut-out from going lean. Modern slide carbs like a Keihin FCR have all sorts of circuits and features to try and improve transient fueling, but it's still difficult because of the changing venturi flow.

That's why most later production bikes come with CV carbs. The slide attempts to keep the velocity of air through the venturi constant, and then control fueling purely with the needle.

[PeWe]

Weber is known as a very good carb manufacturer possible to jet very precise for the actual engine's need.

Stock CB750 round carbs must run a little bit too rich to be able to respond on increased throttle with more air to not fall to its nose

Weber has different sizes of rings to change for best action in the venturi where the underpressure sucks fuel... Largest hole not the best thing.

Check Weber 40 DCOE, 2 port version x2.
https://classiccarbs.co.uk/wp-content/uploads/imported/0/WEBER-40DCOE-151-CarbCarburettor-NewGenuine-twin-40-WEBER-jetted-to-your-spec-221939559590.jpg

An old construction that look really hot.
CB750
https://www.lynxauto.com.au/honda-cb-four-750-motorcycle-twin-40-dcoe-weber-conversion.html

Ferrari used Weber in the carb era.  They look tough with 8 or 12 stacks vertically (6x2 ports)
That's porn!!!
https://www.influx.co.uk/wp-content/uploads/2012/05/ferrari-250-tr-engine.jpeg

Injection look boring if seeing anything of it except for fuel lines and small injectors.