Spark Plugs 101

Here's one that is frankly on the verge of being a little embarrassing. When I bought my first Knucklehead nearly 30 years ago it had a set of Champion D14 plugs in it. For about the next 20+ years, whenever I replaced plug on any of my Knuckles I would simply go to my local Napa and buy another set of D14s.

Then somewhere along the line, I became aware that the Champion D16 was the correct cross reference for the Knuckle. So, after all those years I was faced with no longer being able to remember which number was right and which was the one I had used for so many years. Have I mentioned lately that its no picnic getting old?

So for the last couple of years, every time I have been asked for a spark plug for a Knuckle, I have not been able to remember which was correct; D14 or D16. That all changed the other day when I was researching something else. I happened to run across this in Palmer's "How to Restore Your Harley Davidson":

• "Of the original Harley-Davidson 18mm spark plugs, the No. 3 is most often used. For a motor used mostly on the highways at fast speeds the No. 4 plug is more desirable."

And a few lines later:

• "A cheap alternative to the No. 3 and No. 4 18mm plugs are Champion D-14 and D-16 spark plugs, respectively."

Kind of reminds me of the old line "I used to think had made a mistake once, but I found out I was wrong." So, as it turns out either the D14 or D16 is an acceptable plug in Knuck, depending on the use.

I do think I have uncovered a small mistake in the Palmer book though. All the catalogs I have show the D16 as the replacement for the No. 3 plug. This is backed up by a Champion spark plug catalog that I have. The D14 is colder than the D16. The confusion no doubt stems from the fact that in Champion's heat range numbering the lower the number the colder the plug, and Harley did it the opposite way. That's a very minor discrepancy given the huge scope of his book. I have trouble not transposing stuff in just one short blog entry! The important thing is that there are interchanges for both the No. 3 and the No. 4 Harley plug.

With that in mind, here is a page from the Knucklehead service manual.

This drawing illustrates spark plug heat ranges pretty well. A spark plug's heat range refers to how well the plug dissipates heat. A colder plug dissipates the heat quicker, and so runs cooler. Therefore, a hotter plug will help keep deposits from fouling a plug if used in an over rich or oil consuming engine. On the other side of the coin, a colder plug will be less prone to overheating and causing pre-ignition in a high compression engine or one that is run hard (Both high compression ratios and prolonged high speed will generate more heat).

Interestingly, the factory manual states that:

• " In some cases best results may be found using a colder plug in one cylinder than the other. In this case it is usually the front cylinder that takes the colder plug as this cylinder is not as likely to foul a plug at low speed."

I've never tried it, but it seems logical enough. So next time you inspect your plugs and find they are not both the came color, it may be worth your while to try a different heat range! Now you know.

Local Harley Legend Passes

Bob Hofmeister, a Harley legend in the Minneapolis/ St Paul area passed away at the age of 91 this past week. Bob was a very active member of the motorcycling community for his entire life, and in his "retirement" owned Faribault Harley Davidson. For a short obituary, click here.

Bob was also honored by the motor company, being included in their list of the pioneers of Harley Davidson. Years ago Bob treated me to a tour of the business that he founded, Milhoff Steel, and let me tell you, it was a machine shop with a capitol "M." Particularly memorable to me was a lathe that held an approximately 6 foot diameter piece of round stock. That lathe by itself was far too large to even fit in most machine shop buildings. Yet it was only one of many pieces of equipment. His shop was known as the place to go when no one else could do the job. Bob was famous for his work ethic and customer service.

In his younger days Bob was active in hill climbs, scrambles and TT races. He evidently passed those skills on to his son Bill, who has likewise become a local legend in flat track racing. You may recognize his name from my previous posts here, and here.

On a personal note, I need to mention that Bob had a hand in building the first set of Knuckle heads that I used for drag racing. His good friend Gumps Riley had machined the heads and port spigots for dual carbs, but took them to Bob for welding because he felt that Bob was slightly better with cast iron. Years later when I mentioned to Bob that he had welded those heads which were on my bike for two national championships, he replied with a smile that he guessed he should have charged more.

This past Friday the funeral was held, and as part of it, many great stories and memories of Bob's life were related. I was proud to be one of what I would estimate to be well over a hundred riders to escort Bob Hofmeister on his final trip from church to cemetery. All of those Harleys following in solemn procession from one side of the Twin Cities to the other was a fitting tribute to one who had such an impact on the sport throughout his life.

Lieske Qualifies #1 in SuperGas at Sturgis Nationals

Heating the rear tire.

Congratulations to Joe Lieske, who had a pretty good outing last week at the 2008 AHDRA Sturgis Nationals. Riding his back up bike, a V-Rod Destroyer, he was the number one qualifier in the SuperGas class. SuperGas is a class with a 6.40 index for 1/8 mile tracks. Joe qualified right on the money, running a 6.40. It doesn't get any closer than that.

Joe made it to the semi-finals where he was defeated by only .002 of a second. Pretty close!

Here is Joe during opening ceremonies being introduced with the #1 qualifiers in the other classes. Joe is the one in the orange leathers.

Besides Lee's Speed Shop(that's me), Joe is sponsered by PMFR, Faribault Harley Davidson, and American Thunder.

How Strange

Continuing my series of posts taken from my great grandfather, L.J. Schlattman's book of poems "Gleanings from Life", here is one that illustrates how little things have changed since this was copyrighted in 1926. Despite a few of the words being unfamiliar to us, all of creation still cries out to us testifying of the Creator, and yet man, insignificant and arrogant, still rails against Yahweh, denying his handiwork.

HOW STRANGE

Beautiful star, so pure and bright,

Shining above with your silvery light;

Where have you been, and what have you found?

Where did you get your silvery gleam?

" 'Tis the reflex of God," said the star, "I ween."

Wonderful Sun, with radiant face,

Sending your rays through endless space,

Warming the earth, giving life and light;

King of the universe, wondrous sight,

Whence did you come? with amaze I cried.

"I was kindled by God," the sun replied.

Universe wonderful, endless, grand,

Viewing thy magnitude, dumb I stand;

Who was they architect, who holds sway,

Guiding thy destiny, day by day?

Sun, moon and stars as they circled by,

Answered, " 'Tis God, He rules on high."

Wonderful man with master mind,

Scanning the universe, proud, refined,

Delving in science deep and high,

Tell me, who made you? Who rules the sky?

"Oh," said the man with a foolish grin,

"Chaos and monkey and man are kin."


By the way, I looked up the word "ween" so you wouldn't have to. It means: "To think; to imagine; to fancy. The sense is to set, fix or hold in the mind." That definition is from the 1828 Webster dictionary. Just thought you'd want to know.