Engines Part 4- Reassembly!

The Workshop Manual has step-by-step instructions for both the disassembly and reassembly of Heinkel engines and other  components. The drawbacks of the manual include odd translations and phrasing that doesn't always make sense, or archaic terms (have you ever used “engine shellac”?).  You still need the manual, but  I suggest you supplement it with the following documents:

1. Your own pictures and notes
2.  Exploded parts diagram
3.  Workshop Manual
4.  Articles from Heinkel-Trojan Club Cruiser News and/or Heinkel Club of Germany Newsletter

Stripped Engine Case ready for reassembly

The Heinkel-Trojan Club Cruiser News has some great step-by-step write-ups of most procedures, often complete with pictures. If you are a club member you can buy the complete sets on CD (I think there are three CD’s for 15 pounds, which also contain the excellent document.  “How to Heinkel and Win the Trojan War” (great drawings and information).  They are yet another reason to join the Club if you haven’t already!  The Heinkel Club of Germany magazine usually has a technical article about scooters or cars, but they are in German so their use is limited for me.  Another good source of technical information is Mike McWilliams’ HeinkelTourist.com site.

I’d like to point out several articles that I referenced frequently in my teardown and reassembly process. They’re all from the Heinkel-Trojan Club’s Cruiser News:

1. The Heinkel Engine; Starting and Battery Charging: Sept.-Nov. 2002
2.  Testing the Circuits of the Siba Control Box: March-May 2005
3.  Splitting and Rebuilding the Heinkel Engine’s Case: Dec. 2003- Feb. 2004
4.  Tips on Repairing Exhaust and Manifold Studs and Fitting the Exhaust: June-August 2002

If you’ve never reassembled an engine there are a few steps that may seem insurmountable, but with time and patience you can get through each of them successfully. Here they are, roughly in the order in which you will need to complete them:

Inserting bearings into engine cases and swingarm: At an engine factory, bearings are press fit into the cases using large equipment. Without such equipment you will need to heat the engine case pieces to about 180-200 degrees F.  Your choices are to get some kind of hot plate (I wouldn’t have any idea what to get), heat them up in the oven (not in my house; my wife would not forgive me), a torch (chance of distortion), or the gas grill. I chose the gas grill because it provides even heat and the odors can be easily exhausted.  Heat the cases on medium low for about 15 minutes, and then remove them from the gas grill. Put the hot cases on a large, solid, wooden work surface. Then, hammer the bearings in place carefully and evenly with a block of wood and a big (2 lb.) hammer . Some people freeze the bearings first to slightly reduce their size. I find that once you take them out of the freezer they start to sweat. I freeze the bearings for other applications, but I find in this case its generally more trouble than it is worth.

Gearbox:  If you like puzzles you will get some minor enjoyment out of gearbox reassembly.  Here it pays to take a picture each time you remove a part, and then print out the pictures in reverse order. I would also note which ways you had to angle the various shafts and spindles to remove them, because you will need to do the same thing upon reassembly. After you have all of the gears in place, you should attempt to operate it and be 100% certain that every gear can be accessed. You may want to temporarily assemble the case halves (no need to put in the big timing gear or crank) and make sure I can operate through all of the gears. You don’t want to have to disassemble later.

Leaks: Proactive leak prevention is your final engine assembly challenge. Heinkel engines are notorious for leaking. The main cause of this oil leaking (in my opinion) is the use of very long engine assembly studs that pass through several parts of the case and are secured with nuts on the exterior of the cases. The oil, under pressure in an operating engine, blows out along these studs and onto the vehicle or your garage floor. That’s not the only place you can get a leak, but it’s the one that has stymied me on four engine rebuilds to date. Once the engine is together you’ll have to live with the leaks if you don’t fix them now.

Prime Leak Areas- Make Sure They're Sealed!

I seal these areas too

Even though you’ve probably purchased a complete set of gaskets, you’ll need to take precautions in a few areas. Here goes:

1. Engine case halves. These were precision machined and press fit together as matching pieces with no gasket material (at least that I’ve seen). When you rebuild I suggest using a thin layer of gasket sealant. I’ve never had an engine leak from a case seal after reassembly when I’ve used sealant.
2. Various studs: I know where the issues are but I can’t save that I’ve solved them all successfully. What I’ve been doing is assembling the halves and , then shooting the gasket sealant in, then reassembling. The pictures below show the notorious leak areas. Some people have make tiny gaskets. Maybe I’ll do that next time.
3. Another place is the oil dipstick. The existing seal is usually brittle and doesn’t do a proper sealing job. Buy a new seal and install it.
4. On the clutch cover, install a new mushroom valve. You can read more about this procedure on Mike McWilliams' repair entry here.

I could go about engines forever. I like working on them, they’re big (but not too big), complicated (but not too complicated)  projects that makes you feel like you've accomplished something when you’re done!

If you have any questions on engine reassembly, drop me a line.