Fuel Consumption

[otis71]

I have a ULH that runs good and seems to be dialed in just fine but fuel consumption is at best 25 mpg. Any knuckle or pan I’ve owned has been way better in comparison. Are flatheads or at least 80” flatheads known for this or is something off?

[T. Cotten]

... or is something off?

Odometer?

....Cotten

[otis71]

Four gallons won’t give me quite 100 miles if that’s what you’re asking. That includes all of the reserve.

[T. Cotten]

That's about what I got, Otis,...

With a fully loaded sidecar!

...Cotten

[otis71]

So back to the question-I should expect better on a solo?

[dukekleman]

Otis,

I don't have the experience of running tanks of gas (long trips) through a Big Twin Side Valve motorcycle...

I have done a lot of long trips on Panhead and Shovelhead's though and they are far more efficient than that!

I'll add this, when consumers and manufacturers check fuel mileage there are several factors involved in the results seen. I'm not sure about the driving speeds and scenarios of your particular situation I guess.

Keep in mind that various throttle positions on the carburetors throttle disc result in different AFR's... either way I would expect better mileage than that.

Duke

[T. Cotten]

So back to the question-I should expect better on a solo?

Plenty of room for improvement, no doubt, Otis!

Let us try to identify variables (other than 'tuning') for now.
My example illustrates payload plus wind resistance are big factors. And we know road conditions and riding habits factor in.

If we dismiss mileage-sucking ethanol fuels and other things we cannot control, we are back to 'tuning'.

Please beware of arbitrary over-enrichening to put color on the plugs.

....Cotten

[JoJo357]

Hello Doug, just for comparison, my stock 1946 model U will average between 29-35 mpg. If I baby her, i've squeezed out 42-45 mpg. I believe the ULH is 5.7:1 ~ and the U is 5:1, so not much difference in the compression ratio. I weight in about 175#, and this is with no additional weight on the motorcycle. Just a thought, I had a small manifold leak once, and it robbed some gas mileage till I found it. Also, with the low compression, you can run straight pump gas, but I burn the recreational *(R90) unleaded fuel. Sometimes if I can't get the R90 octane, i go for the premium or mid blend. Sounds simple, but what tire pressure are you at? And yes, my pans & shovels did better on the gas mileage. *Hope this helps Doug.

*M.A.D.*

[Rubone]

I consistently get 25-28 on my 44UL, it is a 3&R gearbox and has always had the hack attached since I built it up in 1977. Even loaded with a passenger and luggage it is near 25.
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