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

In celebration of being back online and on my new server, I thought I would take a pass at making a new logo for the site. I tried to tie in the new Corsa shield design with all of the old Guigaro-designed logo from the 80’s. Enjoy!

My new Ducati Pantah logo



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 74mm
Stroke 58mm
Capacity 498.9cc
Compression ratio 9.5:1
Max power 45HP @ 9050 rpm
Max torque 40.2 Nm @ 6300 rpm
Max engine speed 9500 rpm

Valve Timing

Induction before TDC 50°
after BDC 80°
Exhaust before BDC 75°
after TDC 45°

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″)