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

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.


The stock plugs in the Alazzurra 650 engine were NGK BP7HS spark plugs.

I replaced the stock plugs with Denso Iridium IWF22 plugs. I had these in my 1974 Land Rover, and have them in my Jaguar XJR as well. I really started using them in the Land Rover and they were the only plugs that ever really ran smoothly in my 2.25L. I haven’t done any other experimentation in my Pantah, and I am sure cheaper plugs will work equally well. Let me know if you have had success or failure stories.
Or visit the Official Denso Iridium page.

Other spark plugs that will fit the Alazzurra 650 engine: (these links go to … no affiliation)

  1. Autolite options
  2. Champion Options
  3. Denso Options
  4. NGK Options
  5. Splitfire Options

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.


Twin-cylinder, 90° L-type configuration, 4-stroke, air-cooled, mounted on closed double cradle frame.

Bore 82mm
Stroke 61.5mm
Capacity 649.5cc
Compression ratio 10:1
Max power 56.5HP @ 8400 rpm
Max torque 40.5 lb. ft. @ 5750 rpm
Max engine speed 8900 rpm

Valve Timing

-612549 +612550
Induction before TDC 40° 39°
after BDC 70° 80°
Exhaust before BDC 67° 80°
after TDC 43° 38°

Operation and clearance of tappets, cold motor condition:

Intake and exhaust opening rocker arm 0.10mm (0.0039″)
closing rocker arm 0.00%0.02mm (0.00%0.0008″)