Old scooter - New gas?

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Ripley/Fla

Old scooter - New gas?

#1

Post by Ripley/Fla » Wed Nov 21, 2007 1:51 am

I am going to buy a pan. Can you run one on unleaded gas? I've been looking around and have seen bikes that have heads reworked with new seats/valves (shovelhead?) to take unleaded gas. Is this a standard modification? Sorry if this is a obvious question, but I have not owned or ridden in 25 years. Thanks in advance for any information!



VT

#2

Post by VT » Wed Nov 21, 2007 3:01 am

Sure run it with unleaded.. I ran my '59 for 50K on hi-test non-leaded and a 1/2 oz (half a 35mm film cannister) of Marvel Mystery Oil in each side of the tank. (1oz. per 2 or 3 gallons). My heads were still running okay when I took them off. I though maybe later on in their life, the power was beginning to flatten out on long gradual uphills.... getting into the foothillls. The engineer at Mavel told me that Mystery oil in the gas, would cushion the valve when it closed on the seat. Guide protection too. Run it till it quits.
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#3

Post by Ripley/Fla » Wed Nov 21, 2007 3:18 am

Vintage Twin, Thanks for the answer. I could have used this type of forum before - well there was no internet then!!!! Being away from bikes for a long time and now looking around has led me to a conclusion. The new Harleys, although heavily marketed and zero-down financing, have zero soul.

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#4

Post by john HD » Wed Nov 21, 2007 4:13 am

yes you can run unleaded and add marvel mystery oil. i have been doing it for years.

the vintage avaiation crowd has been doing this for years as well.

one problem you may run into is the digestive nature of todays fuels, if you have a stock fuel system you may need to change your float and possibly the float needle if it is rubber tipped.

there is a member here that is an expert on these issues. and i expect he will chime in shortly....

you came to the right place to get your answers, please take a couple of seconds to join up if you haven't already!

welcome aboard.

john

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#5

Post by FlatHeadSix » Wed Nov 21, 2007 5:28 am

I sure hope they run on today's pump fuels, what choice do we have?

If everything is right, and tight, they run just fine. With or without the Marvel Mystery Oil. I won't be a wet blanket, there's a bottle in my saddlebag too, I can't prove that it helps and I sure can't prove that hurts anything either, but I add it religiously. Nothing wrong with a little voodoo.

One thing for certain, they don't run at all with an empty tank. Go ahead John, post another picture of my bike with that gas can sitting behind it!

The point is that you don't need to make any radical modifications to ride a stock pan on a regular basis using modern unleaded gas. There are plenty of us doing just that. Kind of like the Energizer Bunny, they just keep going and going and going.....

mike

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#6

Post by john HD » Wed Nov 21, 2007 2:28 pm

oh you mean this one?

john :D
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#7

Post by Pantony » Sun Nov 25, 2007 12:02 am

Wonder what happened when he fired that bike up with the can right by the exhaust. Anyway I had my hardened seats installed when I built mine and always ran it on straight regular unleaded-87 octaine, no Marvel oil. In 1948 this wasn't available so I figured the 7.5 to 1 compression was plenty. I did some reaserch and found the run-of-the-mill gas was around 76 octaine back then, with lead of coarse.

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#8

Post by partshunt » Tue Nov 27, 2007 10:40 am

I'v been using a lead additive made by "Gunk". Has anyone been using that or is it useless? Be hard to know till you run up 50,000 miles or so on it I be thinkin...

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#9

Post by Cotten » Tue Nov 27, 2007 1:14 pm

Pantony!

I doubt the 76 octane fuel had any lead.
When tetra-ethyl lead was added, it raised the octane dramatically, and it came out of the pump called "Ethyl".

....Cotten

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#10

Post by Guest » Tue Nov 27, 2007 2:28 pm

I believe regular gas was a minimum of 89 octane....back in the day....wasn't it??????

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#11

Post by Cotten » Tue Nov 27, 2007 4:04 pm

First, let us remember that "octane" is a rating given to a fuel based upon it ability to resist pre-detonation, or "knocking".

Traditionally, these values were determined with a special design of variable compression motor, but they seem to have gone nearly extinct. I fear ratings are now achieved by indirect analysis, compounded by politiks and greed. The result is that yesteryear's numbers just do not equate to today's. (Just like a modern 1/4 HP electric motor won't do half of what a vintage 1/4 HP motor can do.)

Yesteryear's 76 octane could have easily been equivalent to today's 85,.. I suspect.

Remember also that the USA demand for higher octane fuels increased as highways improved after WW2. By the mid 1950's, flatheads were becoming outmoded enough for the petroleum suppliers to shift to producing more for powerful OHV and hemi-headed autos, and slowly dropped the agricultural grades from their pumps.

(And the extremely refined grades as well... remember when you could buy "white gas" at your local "service station"?)

So, "back in the day",... fuels varied widely.

The cost of USA fuel production today could be greatly reduced if 'designer' fuels were dropped entirely, and all the pump gas was made the same. There never used to be a need for "winter blends" or "Intake Valve Deposit inhibitors."
But no one is lobbying for that.


....Cotten

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#12

Post by FlatHeadSix » Tue Nov 27, 2007 6:20 pm

Back in the day, let's make it D-Day for this response, the standard for military MOGAS (motor fuel) was 80 octane. When they began stockpiling for the invasion of Europe in 1944 the production board and quartermaster corps stipulated that a single grade of motor fuel would be produced and distributed; 80 octane. As Cotten mentioned, the methods of measuring and reporting octane rating numbers are not always reliable. There have always been 2 methods; a lean and rich or high and low, standard practice during WWII was to use the high number. So, the 80 octane MOGAS was probably more like 74/80, or closer to 77 octane using today's reporting standards (r + m/2)
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#13

Post by FlatHeadSix » Tue Nov 27, 2007 6:23 pm

the attachment in the last post is from the Army TM (technical manual) for the WLA, here's another clip
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#14

Post by FlatHeadSix » Tue Nov 27, 2007 8:04 pm

Cotten,

I meant to include a comment about the lead. The 80 octane MOGAS and the commercial pump fuels of the same grade most definitely contained lead. Average octane ratings a decade earlier, in the 1930's, ran somewhere in the mid 40 octane range. Everything on the highway back then was running a low compression flathead; cars, trucks, motorcycles, so it didn't matter. The only way they could boost it into the 70-80 octane range was with tetra-ethyl lead. In fact, 80 octane was about the upper octane limit that you could achieve with lead boosters. The way they finally achieved octane ratings above 100 was to selectively refine and distill a higher grade, higher yield crude oil.

The quest for higher octane was directly related to the need for more power, mostly for aviation. The easiest way to get more power without increasing displacement is to raise the compression. Pre-detonation robs power (knocking and pinging) so you have to have anti-knock fuel additives to raise the octane rating. You can achieve the same thing with alcohol, or even plain water if you atomize or mist it into the intake manifold, but tetra-ethyl lead was quick and available (and legal) back then.

some useless trivia for your Tueday.....

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#15

Post by Cotten » Wed Nov 28, 2007 2:09 am

Mike!

So, since modern USA pump gas is rated well above 80, "lead" really is a dead issue?


....Cotten

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