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



Image courtesy of Ducati S.p.A

Markings indicate ZEM type 3504 64.







Unscrew the fixing screws and pull out the starter motor. My Ducati Alazzurra 650 starter type is SU022.





When you remove the connecting rods, be sure to mark the top and bottom halves with permanent marker. This way, when you reassemble them you can guarantee that they will be correctly balanced. Don’t forget to mark which one is attached to the vertical cylinder and which one is attached to the horizontal cylinder. On the Ziploc bag, draw the arrangement of the connecting rods in relation to a marking on the crankshaft as well. When you go to put them back in a few days-weeks-months-years it will help ease the fear that you are not reassembling them correctly.


Markings on top of standard pistons pulled from a 1986(?) Ducati (Cagiva) 650 Alazzurra engine have the following markings:

  • 82-67677A => (arrow) on the top
  • “A” logo on the inside
  • Made of aluminum
  • 3 rings (2 sharp metal, 1 with a spring in it)






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.


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:



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

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

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.