Twin-cylinder four-stroke air-cooled rebirth of a Ducati 500SL

Markings indicate ZEM type 3504 64.
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Unscrew the fixing screws and pull out the starter motor. My Ducati Alazzurra 650 starter type is SU022.

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After unpacking the engine from the shipping crate, I started by degreasing some of the main parts that I could separate. I took off the engine covers by using allen sockets and a 3/8″ socket wrench. The cylinder heads were already separated and in a different box. The clutch was already dismantled. In fact, I don’t think many of the parts that came with my engine as a whole were actually part of the same engine. No matter. They are all from a 650 and I am not doing a “historically accurate” restoration.

I used a citrus degreaser and a plastic scrub brush that I found in a hardware store near the paint stripping section. It has nice short stiff bristles, but won’t scratch the aluminum. I used a whole can of degreaser on just these 4 parts, so I would suggest 3 cans if you plan on doing the whole engine.

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Clean the parts away from where you will be working. That run-off never really goes away. It smells nice, but it is real messy and thin melting grease seems to get everywhere. You can see pics of my top-notch restoration clean-room under the porch here at my house:

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It would be great if someone could fill in the gap on how to start degreasing and prepping your engine when you remove it from the bike. Mine was already partly-disassembled so I am missing some steps. Please e-mail me if you remember to take some pics before starting! Thanks.

Remove the cylinder heads

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The next step would be to remove the cylinder heads by loosening the head nuts with an open-ended wrench. As my heads were already removed, I hope someone can help fill this in for me. [INSERT HOW-TO REMOVE HEADS]

Remove the cylinder liners

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After removing the heads, the cylinder liners should be removed. These can sometimes be assisted by tapping them with a dead blow hammer. If the hammer has two striking surfaces, use the soft plastic or rubber side when striking the cylinder liner to prevent damage. Be careful when removing the cylinder sleeve from the piston as not to damage the surface of the piston by dropping it on the sharp edge of the engine block after the liner is removed. My liners came out quite easily. Let me know if you have trouble removing yours and if you have other suggestions for removal.

Setup (do this first)

The first thing you should do is to get your work areas setup and ready for action. This sounds like an obsessive detail, but as i am writing this after going through the dismantling part, I wish I had taken more time to get ready before starting. So, this short list of things should be on-hand and easily-accessible before starting.

The reason this is important to do before starting to do anything is that whatever you choose to start with, it inevitably involves some form of disassembly. Even with the best of workshop manuals, it can be hard to figure out if that tiny “clink” you hear in the corner of the shop was a mouse, or the tiny spring loaded ball that engages the clutch cylinder you just disassembled. I found this works pretty well:

  1. Think about what you are about to do
  2. Use the right tool to remove the part. Take your time!
  3. Document the parts and their proper location with a digital camera
  4. Make notes on shim, bearing, and special screw locations in a notebook
  5. Place the parts in a common plastic bag
  6. Label the bag immediately with the permanent marker
  7. Move the bag to the disassembled cardboard box for later

Once you have this setup ready, you can move on to the degreasing and minor disassembly phase below. I realized part of the way in that I would have benefited from being more organized at the beginning. Trust me, you only label the bag if you can find the damn Sharpie. I have about 15 bags with parts that are unlabeled. Keep everything organized at the beginning and it will all make sense at the end.
Initial degreasing and cleaning

One of the first things you need to do when starting out is to get everything as clean as possible. It helps keep everything organized as you disassemble. It helps prevent scratching your tolerance surfaces with dirt. And overall it helps you force yourself to stay organized, clean, and methodical. It is easy at this stage to start dismantling everything your socket will fit on. Trust me. This comes from hindsight.

Clean the exposed surfaces of the engine, taking care not to drop dirt or grime into the piston openings if they are open, and give the engine a once-over before undertaking your first steps in degreasing. You can view my page on degreasing here.

I have found it very helpful to keep a bunch of cheap packing paper and an abundant supply of old towels (thanks Lindsey!) around when disassembling the engine. When I took an important piece off, I would take 1 minute to make sure there were no extra shims attached, no o-rings stuck to the back, and no loose bits hanging off before storage.

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After that, I would wrap the piece in brown kraft paper to help absorb oil, and prevent damage that might inevitably occur when stored. I found that I moved the pieces around quite a lot during the disassembly phase. When it is time to send things to have them glassbeaded, you have to search through your big boxes to find the parts you are looking for. Oftentimes I found myself moving delicate parts far too roughly. I made it a habit to wrap everything with paper after dinging my oil pump with the cylinder heads. Nothing major, just annoying.

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If you take the 30 seconds it takes to wrap the pieces in paper, when you open them to do something, you tend to put the paper back on. It’s a simple idea that helps keep the high-tolerance surfaces safe. Everything is protected when assembled, but when you take the engine apart and have pieces lying around all winter, it’s good practice to protect them. I have a huge collection of old towels thanks to my girlfriend wife, so I keep the heavy bits that can damage other things wrapped in a towel as well. Luxury I tell you, luxury.

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Lastly, with the supplies I mentioned on the disassembly page readily available, this is a picture of how I was storing parts. The second I took something apart, I made sure that all of the associated shims, bolts, springs, etc. were placed in the same bag. I labeled everything, even if I know what it was. In the 8 days since I started, I already have forgotten where some things used to go. I have the manual, but I am sure I won’t remember which 0.002″ shim I have on the benchtop when Spring comes.

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Once I have everything bagged, I put it in a cardboard box. I have been keeping 2 major boxes: one for parts outside of the engine case, and one for everything I take apart inside the engine case. Not sure if this will help, but the major assembly process had me searching through my 1 box to find a tiny part having to move the majority of the bags in there to find it. Perhaps it’s OCD, but I added a second cardboard box to help. Call me crazy.

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Begin by removing the spark plugs from the vertical and horizontal cylinders. This is a straightforward procedure unless the plug is corroded in the head.

Ducati provides a spark plug removal tool in the tool kit that comes with each bike. This is a pipe-like tool with a hex formed at one end and a hole through which the handle is placed. It fits, it works, but it isn’t the best choice if you have access to a shop.

I use this socket set from Sears and a short 3/8″ extension on a socket wrench to remove plugs. The spark plug sockets have a rubber insert that holds the plug in place when you remove it. It works equally well when inserting plugs. The main benefits are that you don’t drop the plug and knock dirt and grime into the plug holes and it also prevents changing the plug gap if you drop the plug while inserting it. Both of these things fall into the “I probably won’t fix it” category.

Using the right tools for removing a spark plug may not seem like a big deal. The second you snap off the head of a plug or crossthread the head, you’ll make sure you have the proper tools. I have done both over the years. I am always wary of using a socket extension that is too long. Whether you are loosening or tightening the plug, a 12″ or so extension tends to angle itself on the plug and can result in a snapped plug.

If you are not planning on rebuilding the engine, make sure to plug the holes with a cork or rubber stoppers to prevent dirt from entering. Grime tends to collect aroud the plug holes and removing the plugs usually knocks nasty stuff down there.

Be sure to check out my page on sourcing replacement spark plugs here.