the quest for better MPG

[GARTHXS]

Couldn't hurt.

[kevxs]

indeed, i just ordered the tool!

[DaveT]

One thing I’ve found regarding MPG figures; the XS engine is so poewerful and torquey, the natural inclination in town/traffic/slow riding is to short-shift it and let the low-end grunt move you around. That involves running the RPMs at less than ideal for fuel mileage and at a more open throttle position. Both of those will result in far more than normal fuel consumption. The XS has an ‘ideal’ RPM range for the best MPG.

I can remember ‘back in the day’ when I was a dealer seeing a graph chart that showed torque, horsepower and fuel consumption at various RPMs. According to that chart, there was a definite sweet spot for fuel use.

[kevxs]

i would say probably do shift too early, i prefer to keep my revs down around town but I'm curious when is the ideal shift point and what is the sweet RPM spot for max MPG ?

[jetmechmarty]

Adjust your valves.

[DiverRay]

+1 what Marty said! Adjust them so they are on the "loose" or open side. Then reset the idle mixture and sync.
3,500RPM seemed to me to work best for shifting. It keep the carbs from going too deep into the mains. Above about 5K RPM you are just starting to really suck fuel.

[motoman]

+1 what Ray stated. As for a constant cruising RPM, these ole' motors are real "happy" at 4,000rpm. But of couse, when they were designed and built, 55mph was the nation wide speed limit. Rode mine from new, many yrs. at those slower constant speeds and 3,800-4,000rpm range on LD rides, two-up riding. Fuel then was definitely better quality, and constantly on LD rides two-up resulted in 48mpg. Not true today with same bike's MPG being in the 35-38mpg range.

[MaximPhil]

Some interesting points raised about MPG.
Cruising at 5000 rpm feels pretty good but sure uses the fuel.
Getting the carbs inn synch helps a lot with fuel consumption too.
Phil

[MPittma100]

My Venturer full bagger gets 42 mpg normally. Have gotten as high as 50 mpg at sea level in Florida. These achievements are at <5K RPM. Over 5K (75-85 mph), for long distances, will yield 35 mpg. I have no desire to run the higher speeds no matter where I am headed. As long as I am getting 40+ MPG, I do not see the need to tune anything.

[Bonz]

Originally Posted by DaveT

One thing I’ve found regarding MPG figures; the XS engine is so poewerful and torquey, the natural inclination in town/traffic/slow riding is to short-shift it and let the low-end grunt move you around. That involves running the RPMs at less than ideal for fuel mileage and at a more open throttle position. Both of those will result in far more than normal fuel consumption. The XS has an ‘ideal’ RPM range for the best MPG.

I can remember ‘back in the day’ when I was a dealer seeing a graph chart that showed torque, horsepower and fuel consumption at various RPMs. According to that chart, there was a definite sweet spot for fuel use.

THE best fuel mileage will be at the largest throttle opening in the tallest gear without lugging it. I.E. 30 mph cruising in 4th or 5th takes a larger throttle opening than running the same speed in 3rd. You run more rpm in the lower gear, but at barely cracked throttle.

The more the butterflies are open, for a given road speed/load, the less throttling loss you get and the more efficient the engine runs. Barely cracked butterflies create more vacuum than more open butterflies, that vacuum is what your engine is sucking against.

Tallest gear without lugging it is the way to go for max mpg.

Read this: http://www.ironbutt.com/ibmagazine/ibmag6-p58-62.pdf

[Jerry]

Originally Posted by donebysunday

I remember sediment bowls from my grandfathers tractors.

Sure, make me feel old. My '48 Ford 8n tractor and '53 Oliver OC-3 have sediment bowls...

One more comment about electrical, one I have made in the past. Check / replace your battery cables as part of maintenance. Corrosion builds up under the connectors and between the strands of wire over time. Replace both the positive and negative cables. You will get faster starts and more voltage throughout the electrical system.