Day 27 The power of scientific theory and clutch handles

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Day 27 The power of scientific theory and clutch handles

Distance driven today: 212 miles / 341 km

Cumulative distance driven: 6,873 miles / 11,061 km

Today’s trip: La Entrada to Tegucigalpa, Honduras



Continued major clutch issues: yes - the paperclip is still saving the day J

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After yesterday’s adventures, and our late arrival to La Entrada in Honduras after the border crossing, we decided to take it easy in the morning. After brunch we started riding toward the capital Tegucigalpa. Almost immediately, the clutch issues started appearing again, despite the heroic efforts of the paperclip. We would drive for 10 min with a functional clutch, and suddenly it would stop functioning altogether! Rather, pulling the clutch handle would yield no resistance whatsoever, as if all hydraulic fluid in the line had disappeared.

Zoe and I would stop, do some hypothesizing and some investigations, and then start riding again, only to discover that the clutch handle would behave normally. However, after a few minutes of riding, the soggy clutch would rear its ugly head. We would stop again, read more in the handbook (but to no obvious avail), and start a new round of hypothesizing. Could there be a leak in the line, causing hydraulic fluid to leak and eventually cause the soggy clutch? But why would it start working again 5 min after we made a stop? Could it be related to the speed of riding, or perhaps there was a correlation to the specific gear we were trying it engage? There was no shortage of hypothesis, but there sure was no explanation in sight.

The theories and hypothesis where many, and my mind started spinning in all kinds of directions. After several more stops, and very thorough inspections of the clutch cable, I could definitely conclude that there was no leak, because there was no visible sign of clutch cable fluid leakage. So what could it be? No mechanical cause could lead the clutch to start behaving in such a way that, one minute the handle would yield normal resistance when pulling, and the next minute it would be soggy with no resistance at all. The mystery just deepened.

At this point I decided to put my professional training in practice! What we had here was a classic case of a displayed behavior, a set of hypothesis that had been tested, and an attempt to construct a theory explaining the cause and effect in a way that could account for the behavior. This is the essence of scientific theory, and this was the time to use that knowledge. It became clear to me that, with no leakage in the system, and the clutch handle feeling intermittently stiff and soggy, there must be something affecting the pressure of the hydraulic fluid in the clutch cable.

The fluid in the line was being subjected intermittently by too much pressure and then by too little pressure. The same paperclip that enabled the broken clutch handle adjustment screw to stay in place, would also cause the handlebar to, when fully disengaged, to pull back a bit too much from its normal position, thus causing negative pressure in the closed fluid line. Eureka!



The solution was simple, albeit a bit tiring. All I had to do for the rest of the day, was to constantly hold the clutch handle with my left hand a tiny bit engaged all the time, and never let it disengage all the way such that it could create the negative pressure in the clutch cable fluid that would lead to a soggy clutch. In other words, once I could form a proper theory of the observed behavior, I could also create a hypothesis which I could then test, and through the power of systematic observation I could then work towards an understanding of the new state of the clutch and, perhaps most importantly, how to go about solve the problem. Solve it that is, until we got to Tegucigalpa. Tomorrow, I really need to find a BMW motorcycle mechanic in Tegucigalpa and get a new clutch hand bar adjustment screw that would resolve this pesky issue.

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