The Kneeslider

Doers Builders and Positive People

Old Bike, New Tool: Giving a 1932 Harley a New (Thermal) Image

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Harley 32 thermal image
Harley 32 thermal image after extended ride

For many riders a motorcycle is not merely a toy, but a doorway to adventure and a tool for travel, commuting and skill building. It’s a focus for intellectual growth and an opportunity for learning.

That learning takes place not just on the road but in the garage, where even amateur mechanics quickly learn that the tools they hold can be as useful, enlightening and fascinating in their own right as the motorcycles they love to create, improve, repair and restore.

That’s why, when I had the opportunity recently to borrow a high-tech new tool to investigate the performance of my restored 1932 Harley flathead, I jumped on it.

It’s a tool you won’t find in many amateur garages: a Fluke Ti32 Thermal Imager, most commonly used to ferret out problems in industrial electromechanical systems. It’s designed to capture images of the infrared radiation from materials that can indicate problems below the surface, like defective, overheated bearings or loose electrical connections. It comes with an intuitive software system that makes it easier to adjust, rework and understand the images. The Ti32 is tough enough for the toolbox, though its list price of near $9000 puts it out of range for casual users. I can’t afford an MV Agusta either, but I’d sure jump at the chance to give one a workout, so I grabbed the Fluke Ti32 to examine what might be going on inside my old Harley.

I had just returned from a 180-mile run on the bike across the North Cascades Highway in Washington State. Though I had it running too rich at first, and its “total loss” oil system metered too much 60W into the crank case, the bike had performed well, but armed with a thermal imager I was curious to learn more.

The image above shows the rear cylinder was indeed running hotter than the front which, quite likely, is normal though it may be something needing further investigation, in either case, the thermal image gives a mechanic information otherwise unavailable to the naked eye.

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In addition to reporting for The Kneeslider, I develop content for Fluke Corporation. The folks at Fluke provided the Ti32. You’ll find more images and the stories on what I found on the Fluke website.

Links: Fluke and more images

Harley 32 thermal image
Harley 32 thermal image just after engine start

Comments

  1. I wonder if a cheap video camera with low-light capability and filters can achieve thermal imaging capability? They already work in the infra-red spectrum (I think?).

  4. Excuse my possible ignorance, (being a water-cooled-I-4 type guy), but wouldn’t the rear cylinder run a little hotter anyway? or should I say the front cylinder run cooler? (air/fuel mix aside) I’d be warmer hiding behind the front cylinder that was heating up and disturbing my airflow. That’s one reason I like to ride out front >wink<
    It is very interesting, though as noted, inconclusive. Post more!
    (What we need to prove that is a thermal image after riding backwards for 180 miles!)

  5. I’ve been using one of these to read the “Comments” columns for a long time now – that’s why I’m much more cheerful now.

  6. Those are nice cameras. We’ve been installing them (actually FLIR brand) in municipal vehicles to scope out unusually hot houses…

    A DIY’er could buy one of those “laser thermometers” for around $50 for similar results but without all the pretty colors.

    -todd

  7. OK, besides the rear cylinder runs a bit warmer than the front one, what do we learn from that cool experience ?

    (love the 180 miles backward idea 😉

  8. Always wondered how an air-cooled inline four managed heat…….they seem to last forever with little maintenance….no anti-freeze….water pump….thermostat…..radiator……temperature gauge……….

  9. A thermal camera is the only way that you could look at a Harley and ever see it being a hot bike!

    • Ouch, Tom!

      Especially true of this machine, 74 c.i. that produces somewhere between 30 and 35 hp. On the North Cascades run I was clocked passing a motor home uphill at 65 mph, which made me mighty proud. I’d guess top speed at less than 80 mph. Think John Deere torque and you won’t be far off. But hey, it’s 79 years old. Where will 95 percent of today’s bikes be at age 79? Recycled into beer cans.

  13. I notice you repeat a common fallacy that a lean mixture runs hot. There is a mixture that runs hottest and it’s just a little richer than stochiometric. It’s the leanest mixture that burns all the oxygen. It’s also the mixture that makes the most power – which figures since the power comes from heat. But any mixture leaner, or richer, than this runs cooler, i.e. the exhaust gas temperature will be lower. The idea that a lean mixture runs hot comes from the fact that a lean mixture can cause burned pistons or valves. The reason it does this is because it leaves unburned oxygen which combines with the piston or valves – not because it produces a higher temperature.

  14. thanks for sharing the info! I’m always curious to hear what temps other early bikes run at. Last year somebody had a digital thermometer (the ones shaped like a gun, non contact type) on a pre1916 run, and measured a few of the bikes. The valves are exposed on the early ones, and exhaust valve temps varied from 450 hundred degrees F to around 615F if I recall correctly. This was after a portion of road where we ran near max speed.