Lunchtime Brain Surgery Break

People who are in the habit of offering advise will always tell you that, in the matter of how one makes one’s living, one should always ‘follow one’s joy’ — i.e. make your living doing something that makes you happy.

This advice, is, like most advice offered by people from whom advice has not been solicited, purest unadulterated horseshit.

Joy is joy. Work is work.

That’s why we call one joy and the other work.


So, a few days back, I was hard at work.

Unsurprisingly, being at work, I was experiencing minimal joy.

Don’t misread me — I’m not for one single second claiming that work is always one giant, soul-sucking bottomless pit of despond.

It’s just that statistically speaking, it usually is.

Today wasn’t bucking any trends, buddy.

I’m a complex personality, an important part of me is An Engineer. Engineers like to think of stuff, but, more importantly, they like to finish stuff.

To Get Stuff Done.

And if you’re struggling for a way to understand this work/joy continuum, one of the reasons work is work is that finishing stuff — that real, pop the Champagne corks and fire up the Cubans moment — happens so infrequently.

Heck, that might even be joy.

Problem is, these moments are separated by a metric crapload of hard, grinding work.


Maybe it’s a Dilbert-style coping mechanism, but when I’m having a tough time remembering the last time I had a “Hot Damn, this sh*t be done! and The Lord Pronounced it Right and Just” moment at work, I will sometimes think hard to identify and then complete something that badly needed to be done, and lacked only my will to attack and complete it.

Think of it as an artificial motivation/fulfillment sweetener.

Or maybe fast food for the beleaguered soul.

Then, having Got Stuff Done, I can look at my face in the mirror with a smile, and sleep the sleep of the righteous when I go to my much deserved rest.


These little joy pellets usually take the form of laying tools on some bit of material reality, and either making something where nothing existed before, or taking something performing suboptimally and making a difference in the quality of its little mechanical life.

That it takes accomplishment outside of work to keep the emotional tank full while at work is somewhat ironic, but given a choice, I’ll take irony over despondency any day.

Anyhoo, in a work period of particular unremarkableness, I looked at my emotional joy indicator dial, and discovered that we were deep into the reserve tank, and in danger of running completely dry.

What was it that needed me?


I had spent a great deal of time going through my R90S last spring and summer, and that meant laying hands on a really material percentage of the parts — both moving and non — in the entire machine.

Fairly early in the process, after I’d essentially stripped the bike, I remember looking at the bare motor sitting transmissionless in the frame and thinking, “I can’t remember the last time I checked the valves on this beast. Well, it’s never going to be as easy as it is right now — the bike’s already stripped and it’s too disassembled to get away. Let’s have at it.”

So I did.

The heads had definitely needed to have their studs retorqued, but given how much more work was queued up, and the non-zero possibility that the bike might not end up running after removing and replacing essentially everything, I’ll admit that I probably didn’t complete the job with my customary zeal for detail. That — combined with the fact that both the battery and fuel tank were on the bench — meant that I also didn’t check my work after completion.

Fast forward about four months, and the bike was indeed back on the road. It shifted well, it ran well, but it didn’t have the same comically wonderful throttle response that it had before the rolling resto.

After playing back that distracted valve service, I knew what had occurred, and I knew what bit of mechanical reality really needed me.


It’s hard to imagine that a piece of machinery very similar in complexity to a Briggs and Stratton lawn mower engine could be sensitive to the smallest niceties of the tuner’s art, but the BMW Type 247 Airhead motorcycle engine definitely is.

In the case of this particular engine, my oversight had been to skip the detailed setting of rocker arm end float before adjusting the valve clearances. What I was confident I would see when I opened the cases was a set of rocker arms with about .002 inch of unnecessary end float in the valve rockers — end float whose result was noise, wear and the reduction of about exactly .002 inch of valve lift in operation. That miniscule oversight accounted for the difference — upon rolling the throttle open — between being kicked in the head by a mule and being slapped in the head by your sister.

They’re both very similar in description, moving mass attempting to vary the trajectory of your noggin.

But they are very different in effect.


So with my large cuppa Joe in hand in the morning, I went to the garage.

I rolled the bike to a position where I had room to walk around, disconnected the negative battery lead, and removed the alternator cover and both valve covers.

Then I went back inside and got into the day’s work.

Having arrived at lunchtime, I grabbed a glass of water, a carb bar, and went back to the garage.

I removed the spark plugs and rotated the engine around to Top Dead Center.

With their 360 degree crankshafts, the Airhead engine will have one set of valves closed at TDC on its compression stroke — which is where they need to be adjusted — and then have the other set of valves closed 360 degrees of crank rotation later.

I located the cylinder with both valves closed and grabbed the intake valve rocker.

Sure enough, it had measurable end float — just enough to turn this tiger into a pussycat.

About 15 minutes with my torque wrench and feeler gauges was sufficient to set everything aright.

Untorque the rockers, squeeze the rocker supports together, and retorque them in the correct position. Set the proper .006 and .008 intake and exhaust clearances.

Rotate engine 360 degrees. Move to other cylinder and repeat.

Replace covers.

Install battery ground, and test fire.

The S came to life with authority. Throttle response at idle seemed noticeably improved. Valve noise was down, and the idle was smoother as well.

Joy. Total investment 20 minutes, or about 10 minutes less than I usually take with a sandwich and the Washington Post.

My serenity levels were markedly improved as I completed my work that afternoon.


Spinning wrenches can be an easy shortcut to achieving joy.

But one doesn’t know if one has really gotten there until one takes a test out on the road.

After work that day, I leathered up, and cinched down my elkskin gauntlets and my Shoei.

Upon turning out of the neighborhood, I headed up MD180 West and started up through the gears. The engine had enough heat in it to take large throttle so, biting third, I rolled it open all the way.

The beast, long dormant, had returned. Barely a third of the way open both ends of the boxer rose hard to top out the suspension, and things picked up from there.

Making a left on Olive School Road, we had the ultimate test. Olive School is one of those Roller Coaster Roads — more or less flat with a series of small hills in line that allow the torquey to pull one power wheelie — or even a jump or two — after another.

At the top of the first hill-let, I rolled the throttle in third and the front wheel came smoothly and smartly off the ground, not returning to earth until I gave throttle back.

Bodhisattva. A Flash of Unadulterated Joy. A Dancing Soul.

The effects of this enlightenment should be sufficient to hold me for several weeks at least.

Wonder when the last time was I bled my brakes, though…



2 thoughts on “Lunchtime Brain Surgery Break

  1. Pingback: Ham Fists, Low Seats and Toilet Parts | Rolling Physics Problem

  2. Nicely written, except that your airhead engine does not have a 180° crankshaft. It has a 360° crankshaft. There is a spark plug firing event every 360° in this engine. Both pistons reach TDC at the same time, one on its compression stroke, and the other on its exhaust stroke. When you said that you found which cylinder was at TDC and ready to have its valves adjusted, what you really meant was that you found which cylinder was at TDC on its compression stroke. The other cylinder was also at TDC, but was finishing its exhaust stroke and beginning its intake stroke (it was on valve overlap). At that point, the exhaust valve is not yet quite shut, and the intake is starting to open. Thus neither is on the cam’s base circle and neither can have its clearance adjusted.

    In contrast, a CL350 Honda does have a 180° crankshaft. In this engine the spark plug firing events are 180° apart, then none occurs for another 540° of crankshaft rotation. When one piston is at TDC, the other piston is at bottom dead center, or BDC. On the Honda, one would typically rotate the engine until the left hand cylinder reaches TDC compression, set that cylinder’s valves, then rotate the engine only 180° and set the valves on the other cylinder.

    Maybe, as an engineer, you already knew this and simply had a couple of typos. If not, you know it now. I hope this helps. Oh, there’s really no need to remove the battery cable and the front cover. You can simply shift into 4th or 5th gear and bump the engine in small increments with one hand turning the rear tire. That is what I do on my old Triumph, where there is no front cover to remove. It works quite well, and the Triumph also happens to have a 360° offset crankshaft like the airhead.


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