Knucklehead MPG

[conwayde]

I've got a '38 Knucklehead that gets approximately 28 MPG. I've asked other Knuckle and Panhead owners about their mileage and they said that's about right. I thought I had read in original manuals that the EL should get about 45+ MPG. Am I wrong here? Were these the gas guzzlers of their day, or is my low MPG the sign of some possible problem?

[T. Cotten]

Conwayde!

Your mileage can be improved, but please be aware that modern fuel's volumetric efficiency is lower than our forefathers enjoyed, especially with ethanol blends.

Some loose ends that you my wish to investigate, however, are such things as micro vacuum leaks, improper float buoyancy, improper mixing within the carb due to a loose venturi and/or excessive throttledisc wear into the bore, etc., etc.

With a light payload (minus windshield, bags, passenger, and all those important other things), I would hope you can achieve ~35 mpg plus, *with all things in order*.

Many report much better performance, but variables are endless, record-keeping poor, and egos enormous.


...Cotten

[Chris Haynes]

My old '47 with a 2.2 gallon tank was good for 60 miles per tank.

[Rubone]

My Knuckle is good for about 30 mpg, M\my UL with hack about 25. 45 is best at about 38. I am at 7000 feet above sea level.
Robbie

[conwayde]

Interesting - I'm sure additional responses will also be all over the map, but it seems 27 to 35 MPG is what people are actually getting. According to the 1936 brochure, "Interesting Fact about the 1936 Harley Davidson", regarding the EL 61OHV, M.P.G. is noted as 45-65! Even with micro leaks and a poorly tuned carb, 30 MPG is still a long way from the estimated MPG.

The handbook recommends "Benzol blended gasoline (about 50% Benzol), Ethyl gasoline or other equally good "anti-knock" gasolines as better motor fuels than straight gasoline." I use 93 Octane, but can even this be that vastly inferior to gasoline of days gone by? Would the use of a leaded additive help MPG any?

[T. Cotten]

ConWayde!

If you were trying to build and sell motorcycles, you would probably inflate their performance stats as well.

You won't find much benzol or benzene added to modern fuels except as a rectification agent to remove water from the silly ethanol.

Many home additives affect the specific gravity of the fuel, thus affecting the float level, so they must be used with caution.

Tetra-ethyl lead was never added for mileage, but to avoid engine knock at the expense of oil life and public health.
(Today's pump additives may have their own health consequences, however we have little choice but to pollute with them.)

My only accurate feed back on mileage has come from Indian Chief riders, as ALL the others took my freebie floats and ran off with them, figuring I would be happy with a "Went to Sturgis and back and it runs good." to fill their promise of recording consumption.
(My "Stiffs List" is still growing, and they deserve a spot!)

...Cotten
PS: A micro vacuum leak may only suck a little of your mileage, especially if you only traverse cow paths and alleys as many of these vintage machines were expected to do little more...

But a stretch of Interstate can turn that micro leak into a hole in the piston. Of course, the piston always takes the blame.
Or when the head warps, its that damn gasket!

...Cotten

[Rod]

'63 Flh Mpg

I can go 90 miles before switching to reserve on my '63 FLH with 3 and 1/2 gallon tank. Anybody know what the reserve capacity is?
Rod.

[koanes]

My 46FL runs consistantly at 44-45mpg. A little less if I have to run ethanol added fuel. Traveling a mostly rural two lane to NE Wisconsin last fall with wife and gear on board, I got 50. Carb was a battered M35tp that got new shaft and bushings, Liberty float and a swedge job to tighten up the venturi in the bore.

[Jerry Wieland]

My 46 EL consistently does 40 mpG and for some reason when I get out west in the Black Hills I can almost squeeze 50 out of it.

Jerry

[Rubone]

So Jerry, what kind of MPG do you get at 40 MPH!!

Robbie

[Rooster]

My 46 EL consistently does 40 mph and for some reason when I get out west in the Black Hills I can almost squeeze 50 out of it.

Jerry

Must be when you're headed downhill, huh?

[bmh]

Unless your compression ratios are 9:1 or higher premium gas is most likely a waste of your money and possibly a detriment to fuel mileage as they raise the octane through additives like more ethanol and such. Any Semi-hemispherical chambered motor with less than 8:1 compression should do fine on regular gas depending on rider habits and state of tune of course. Rider habits and overall gearing for that matter will have drastic effects on mileage as well as if and when detonation occurs. If you roll off the advance a little in high load situations you will be able to use lower octane gas easier. That's what the left twist grip was put there for, not just for starting. There are two types of octane, real & motor. look at the pump and you'll see a formula, Octane = R+M/2. Basically it's an average. Real octane is potential for power, motor octane is resistance to detonation under compression. This is not to say the two are totally unrelated but their relationship varies depending on what specific compound you're talking about. Lead & ethyl increased motor octane and allowed higher compression. Unfortunately these days they raise the stated octane at the pump by increasing the real octane, good for performance if you have a modern motor with all the modern management systems that allow for higher compression, leaner burn with this brew. Keeps the dreaded EPA happy too, but as stated it's not the best for our old motors. Fuel mileage around here seemed to take a real dive about five years or so ago. Mileage on almost everything I own dropped 5-15% overnight, except our fairly new jeep with fuel injection and all, it actually increased slightly. I attribute this to a reformulation of the fuel. Others around here noticed the same thing. My Shovel which reliably got 40-43 MPG it's whole life now struggles to get 38 on a good day, 35 on most. Unfortunately her compression is 9.5:1 and she will not tolerate anything but premium, and can actually tell the difference between certain brands. Some simply will not work as she detonates under load as if they were regular. Not everyone uses the same additives to boost the octane numbers. so I guess my advice is find which brands/octane that work best for your particular machine and habits and try to stick with them.

[LCC]

My 40EL gets a consistent 43 MPG, 45E gets 45MPG. The same going north or south. Larry

[Jerry Wieland]

Rub Thanks for the correction. Jerry

[jke]

I recorded better than 60 mpg with my 93 inch swing arm Knucklehead bagger in route to the Knucklehead Reunion V two years ago. Matt Olsen was on the ride and can verify. In fairness I'll say that we never rode over 60mph as Matt was breaking in Carl's 39 EL . Why not keep track of your mileage on the way to the Knucklehead Reunion VII. Maybe we can conjure up an award ?