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

WORK IN PROGRESS

 

This is a partial list of hardware that I replaced on my Marzocchi M1R forks. Eventually, I will organize this to include both low-cost and fancier metal and coating options. Izaac (from Pantaheads) just turned me on to yellow zinc screws. Now I have to start my list over.

Sources:

  1. Eagle Day
  2. McMaster Carr
  3. Fastenal

 

Rebound adjuster:

  1. #8-15 x 5/8″ Phillips Flat Head Sheet Metal Screw [A4 316 SS]  x 1
  2. Black-Finish Steel Internal Retaining Ring for 17mm Bore Diameter x 1
  3. Metric Spring Steel Shim – DIN 988 0.1mm Thick, 10mm ID, 16mm OD x 1
  4. Metric Buna-N O-Ring 1.5 mm Width, 11 mm ID x 1
  5. Metric Buna-N O-Ring 1.5 mm Width, 5.5 mm ID x 1
  6. M6-1.0 x 20mm Socket Head Cap Screw [A4 316 SS] x 2

 

 

Bottom of forks:

 

Cross brace:

 

These are the markings on the stock seals from my Marzocchi M1R forks.

(in order of assembly)

Dust seal: Marzocchi 41.7 Rolf 4

Metal washer

Stop ring

Oil seal: Marzocchi 3 41.7 55 10 10.5 RP Rolf

 

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

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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.

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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)

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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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