Heinkel Engines, Part 3: Checking and Cleaning

Time to get back to the Heinkel car and scooter engine! I’ve talked about tearing them down and the tools you should have to make your job easier.  Now for two obligatory exercises- Checking and Cleaning:
As I take items apart I measure and inspect them to make sure they are not excessively worn or don’t meet the tolerances specified in the workshop manual. There are a dozen or so pieces to check, which will assure that your engine will run optimally once it is reassembled.
Heinkel Kabine engine parts
Engine Case- testing reassembly
Here’s my list:
  1. Cylinder Head: Make sure it’s flat. You can test this with a piece of glass and a flashlight. Place the head on the glass, and shine a light from the other side. If you can see the light between the head and the glass, you should bring it to a machine shop and have it flattened. Also check that the cylinder studs are tight and not distorted.
  2. Valves: I put grease (or something like it) around the valve seating area and then blow air though the manifolds. If the grease blows right off the valves don’t seat properly. Once again, the answer is “bring it to the machine shop”. They can take the valves apart, make sure they are not bent or excessively worn, and that the guide bushings are OK as well.
  3. Piston and Cylinder Wear: Measure these and compare them to the tolerances in the Heinkel Worskshop manual. If the piston is more than .15mm from the original size you should consider reboring the cylinder and using an oversize piston. This is not unusual; I’m running a 4th oversize piston on my engine. 
  4. Rings: Measure for excessive play, replace if needed. Tolerances are listed in the manual on page 25.
  5. Clutch: I replace the cork plates, and suggest replacing the spring(s).
  6. Drive and Swingarm Chains: I look for excessive wear on the chains. I also check the deflection of the chains. If the swingarm chain deflects more than 1 ½ inches from side to side, then I replace it. To measure, stretch out the chain, lay it on it’s side, then check the deflection.
  7. Brass swingarm journals: Once again you are checking for side to side play. Let these go to long and your car will wander. It is also impossible to replace them unless you totally strip the cases, so now is the time to fix them!
  8. Sprockets: If the tips of the teeth on the gears are not uniform and are very sharp then you should replace the sprockets. Beware, replacing sprockets isn’t cheap! 
  9. Rear Hub Driveshaft: Make sure the parallel grooves are not distorted (usually a sign of riding on a too loose hub) and check the threads (to make sure they weren’t overtightened). These shafts are available from the clubs as well.
  10. Crankshaft: Compare to the tolerances in the Heinkel Workshop Manual
  11. Dynastart: Lots to check here. There’s an excellent article in the Heinkel-Trojan Club Cruiser News Magazine on what to check and how to do it. I’ll mention that in a later article.

As you take stock of these items, add any required parts to your order list.
One amazing thing, at least to me, is that you can get most of the mechanical parts for the Heinkel cars, and virtually all of them for the scooters. This is especially true of the engines, where all of the wear parts are available either new or rebuilt. The youngest of these vehicles is 47 years old. Contrast that to a typical Japanese motorcycle, where after 10 years you may start to see serious gaps in parts availability. I think it is a testament to the dedication of the members of the English and German clubs that this is possible.
Most of the big parts have already been into and out of the parts washer.  My parts washer is in the basement, so I’ve been using a water- based cleaner from Simple Green (which is actually purple color) that does not discolor aluminum and doesn’t smell. Most parts come out of the parts washer relatively clean, although cases and a few other items often have nooks and crannies full of road grime. For those I dig out as much as I can with a toothpick, awl, – insert your sharp instrument of choice here- and then put them back in for a soak.  Depending on how much of a perfectionist you are, you might do this a few times. If you have a fatter wallet or are really trying to make your engine look spectacular, you may want to consider bead blasting the cases. You can use glass beads or even extra fine coal slag (although you’ll have to go over that with a red scuff pad to get it suitably smooth).  A final step could be to use a naptha-based cleaner such as WipeOut, which works phenomenally  well, but is toxic and probably shouldn’t be used indoors.  
My engine cases had suffered from a fair amount of exposure and were pitted at the bottom. So, I decided to bead blast and then put on a high temperature (500 degrees F) clear coat. This setup allows me to simply wipe off the grime,  which has worked well for me.

For small parts, I empty them bag by bag into the parts washer basket. If I’m unsure of how parts are going to be reassembled, I zip tie them together in their respective order. Small internal parts clean up nicely. Sometimes exterior parts need a special session with a toothbrush, but they end up looking good. 

With everything clean and checked, I usually finalize a parts order. Once I submit the order I pack up my stuff in an orderly fashion and wait for the parts to arrive.

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