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.

68 Inch Racer, part 3

In part 1 and part 2 of 68 Inch Racer, I outlined the physical dimensions and bottom end parts for this "dream" motor. In this installment I would like to wrap it up with the top end and valve train.

As to the heads, if I had a set of dual carb Knuck heads laying around (which I do) I would probably use them. After all, if I am going to label this a "racer" then why would I be worried about the leg clearance issue raised by two carbs sticking out the left side of the bike. Intake valves; 2.060". I had a set custom made by Ferrea Racing for a motor I did last winter. Beautiful valves, and no need for a lash cap, but I was disappointed with their limited selection of tulip choices for a 3/8" stem diameter. The only one they offer had more tulip than I wanted, which necessitated shorting the bottom of the guides slightly. It was also quite a bit heavier than I would have liked. Perhaps a 5/16" stem next time with a custom made valve guide.

It goes without saying that the piston domes, exhaust ports and combustion chambers would get the ceramic treatment like this.

Working off a couple of Knuck heads that I have oiled out in the past, it looks as though a head volume of 128 cc is a realistic starting point. Now, if we bore the Knuck heads out for the Pan cylinder's fire ring, we actually increase the head volume by about 5.71 cc's. But of course the fire ring itself will take up most of that increase. The total head volume when bored for the fire ring, but taking into account the amount displaced by the fire ring, calculates to 128.38 cc.

But here is where it gets interesting. The 74" Pan cylinder is shorter than the 74" Knuck by .200" when measured gasket surface to gasket surface (5.530" vs. 5.330). But if you add the height of the Pan fire ring they are the same length. That means that the piston will come to the same point in relation to the gasket surface on the Knuck cylinder as it does to the top of the fire ring on the Pan. But in effect you are lowering the head .200" down by using the Pan cylinder (think of it like shaving the head .200") Now we are talking some compression! When I plug all this into my Engine Analyzer program with a .020 thick copper head gasket, it comes out to 12.26:1 compression ratio. And after double checking all my figures a couple times, it still comes out to that!

Cool. Now we are into race gas territory (68 inch Racer - remember). That kind of compression will allow us to run a fairly radical cam as well. Any time you talk about high performance on a Knuckle engine, in my book there is really only one brand of cam to consider, and that is Leineweber. I am thinking his #3 Knuckle cam. It has .420 lift and 312 degrees of duration, but keep in mind this duration is measured at .020" rather than the customary (for Harleys) .053". That is still probably near 275 degrees duration if converted to .053".

Keeping with the "racer" theme, everything seems to point toward an engine that will not be easy to start. So we might as well add a magneto. I'm envisioning a bike that does not even have a kick starter.

Since this "paper engine" is getting a set of real life vintage dual carb Knuck heads, I would also use a set of real life 40mm Dell 'Orto pumper carbs that I have left over from my first drag bike. They were a little small for the 114" Knuckle, but I suspect they would work well in this application. Since the heads have a 4 bolt Linkert pattern, I would weld flanges onto the Dell 'Ortos to match. Jetting them to run on E85 (85% ethanol) would be really tempting. It has enough octane for this kind of compression ratio, plus the government helps pay for it (with my money). Good luck on getting them to kick in for your $15 a gallon racing gas.

One last thing. If the motor was to be used on the drag strip, then I would leave the valve train open, with no oil going to the top end. This is not a huge advantage, it just simplifies the oiling system and eliminates any clearance issues between spring and cover. But that's the way we used to do it, and it looks pretty cool. For any other application I'd enclose the valve train. Either way I'd use a pre '40 oil pump for the thinner gears and less oil volume in the motor.

That pretty well wraps it up. Did I miss anything? And.... an even better question: will it ever get built?

Faith in God

Here is another selection from my great grandfather, L.J. Schlattman's book of poems "Gleanings from Life".

Faith in God

Have Faith in God, my doubting brother,

Have faith in God, 'twill still your soul;

Pour oil upon the troubled waters,

And lead you safely to the goal.

• 
  

Fear not that faith is superstition,

God's word is but an ancient tale;

'Tis founded on the Rock of Ages,

Eternal truth, and will prevail.

• 
  

Where science halts and critics stumble,

And must admit, "We do not know;"

There Faith in God begins to function,

Illumes the way for us to go.

• 
  

Let science dig with spade and shovel,

With microscope dissect the sod;

Dig deep, dig deep, my seeking brother,

Dig deep enough and you'll find GOD.

• 
  

Hypocrisy and Ism's squabble,

Oft dim the radiance of the Sun;

Have faith, they cannot hide its splendor,

'Twill still shine on when all is done.

• 
  

Let scoffers rail and skeptics mutter,

"Your faith in God is but a tale;"

Fear not, be not dismayed, my brother,

HE reigns supreme and will prevail.

• 
  

When science fails and isms crumble,

When Sun and Moon and Earth shall quake,

When human mind shall cease to function,

And human theories shall break.

• 
  

The God of Abram, Isaac, and Jacob,

The master architect on high,

Will still be ruling all creation,

And faith in Him will scale the sky.

68 Inch Racer, part 2

If you read my post entitled Paper Engines, you will recall that I solved the problem (at least on paper) of building a high compression 61" Knuckle lower end with a 74" top end.

There still are a few things to be considered in the bottom end. For one thing, there is the subject of flywheel weight. That will be partly determined by the end use of this motor. Whether it is for drag racing, "street" racing, Bonneville, flat track, or some sort of road racing. For most of these scenarios, I would lighten the flywheels (the one exception being drag racing with a slick). How much to lighten them is the question. The minimum would be to cut down the heavy left side flywheel to the thickness of the right side wheel.

stock 61" flywheels on left , lightened S&S on right

Bike weight is also a factor here. Flywheels "store" energy, so the heavier the bike, the harder it will be to get under way from a dead stop with extremely light wheels. Still, the gain in the rate of acceleration is too good to pass up in most applications.

Since the UL rods are an aftermarket imported item of somewhat unknown quality, I would at the very least have them shot peened. Possibly polished and shot peened. The purpose of polishing is to remove any possible surface imperfections that could lead to a crack. However, polishing also removes the surface left from the forging process which increases the strength of the rod. Shot peening puts that harder surface back on (so to speak). So, just shot peen, or polish and shot peen, but do not polish only!

Of coarse the rod change alone would dictate that the flywheels be balanced, but it becomes even more critical when lightened.

Since the point of this engine is to turn some RPMs, the crankpin and mainshafts are probably not a place to skimp. S&S makes all of the early shafts, including the stepped crankpin, and are probably the highest quality available. Yes the rod set will come with a new crankpin of unknown origin, but that would be better set aside to go in a restoration that will not see such severe service.

This is to be a "Racer" and not a restoration, so why not take advantage of the built in extra strength of Panhead cylinders. Even bored to +.060 (which makes it a true square engine 3.5" bore x 3.5" stroke) the Pan cylinders are undoubtedly stronger than a Knuck cylinder. Sure, there are reproduction Knuck cylinders that are stronger than stock, but they aren't cheap. I would spend the money elsewhere. Besides, there are plenty of Knuck heads out there that have been converted to the Pan headbolt pattern already, so why not use them.

For pistons, I would start with a cheap Pan/Shovel cast piston which is called a 10:1. The dome volume on them is about 52cc which will get some compression ratio (I'll discuss that more when I get to the heads). Once the domes are ceramic coated and the skirts Teflon coated they should work very well.

More to come.