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Archive: Ducati Darmah DD Engine Strip: part eight

The rebuilt crankshaft land repaired gearbox are fitted in the crankcase halves, as completed last month. Now it’s time to finish the bottom end rebuild. Care and patience are crucial at this stage for the valve timing bevel gears must be assembled with all timing dots correctly aligned. Get it wrong and you'll damage the valves, pistons and possibly the conrods.

• Work commences with the bottom bevel gears on the right-hand side of the engine (pic one).
• Push the two bevel gear shafts into their locating holes in the crankcase just below the bevel support plates (pic two).
• Fit the Woodruff key into its slot in the crankshaft (pic three).
• Push the drive pinion onto the crankshaft (pic four). The two timing dots MUST face outward.
• Turn the bevel gear in the crankcase support housing so the timing dot is facing outwards (pic five).
• It is important to note the position of the timing dots on the two timing pinions. One dot is located on the shoulder of the bevel gear teeth (pic six), the other is on the top face of the straight cut gear (pic seven).

• Push the bevel gear onto its shaft. Ensure the dots on the bevel teeth align, at the same time, rotate the crankshaft to make sure the pinion timing dots align (pic eight). Once aligned and gear teeth meshed, push the gear home.
• Replace the second bevel gear, again ensuring all timing dots align. It’s not as difficult as it sounds, it’s just fiddly, but with a bit of juggling they all line up (pic nine).
• Fit the bevel gear support plate spacer (pic ten).
• Fit the bevel gear shims over the ends of both bevel gear shafts (pic 11).
• Refit the bevel gear support plate over the end of the crankshaft and bevel gear shafts (pic 12), tapping lightly with a soft mallet.
• Replace the four bevel support plate Allen screws (pic 13).
• Push the alternator spacer into place on the crankshaft (pic 14).
• Fit the alternator woodruff key into its slot on the end of the crankshaft (pic 15).
• Push the alternator onto the end of the crankshaft making sure the flat side (pic 16) faces inwards.
• Now fit the alternator tab washer and locking nut on the end of the crankshaft (pic 17) and tighten with a 30mm socket. Prevent the crankshaft rotating by using the method explained in the engine stripdown.
• Knock back the tab washer (pic 18).

This completes the right-hand side. We now turn to the left side.

• Push the starter clutch gear spacer onto the crankshaft (pic 19), followed by the starter clutch gear (pic 20). Note: the starter sprag clutch gear is a loose fit in the clutch gear, make sure it stays in place or the roller bearings will fall all over the garage floor.
• Replace the electronic flywheel woodruff key into its slot and push the starter engaging shaft into its locating hole (pic 21).
• The electronic flywheel can now be pushed into place on the crankshaft over its woodruff key (pic 22).
• Fit the electronic pick-up rotor woodruff key (pic 23) and push the rotor into position on the crankshaft (pic 24).
• Replace the rotor tab washer and retaining nut onto the end of the crankshaft (pic 25). Tighten the nut, stopping the crankshaft from turning as previously explained. Knock back the tab washer to keep in place.
• Place the gearchange return spring onto the lug on the gearchange quadrant (pic 26) and pull the ends of the spring apart, so the spring is on either side of the gear quadrant pin (pic 27).
• Pull the operating arm of the gear quadrant out so that it’s clear of the gear change drum while the quadrant is pushed onto its locating pin (pic 28).
• Make sure the ends of the gearchange return spring are located on either side of the locating pin on the crankcase (pic 29), ensuring the operating arm is located correct on the gear change drum (pic 30).

• Place the shim onto the end of the gear change shaft (pic 31).
• Push the gear change shaft into its locating hole in the crankcase, aligning those marks I told you to make when I dismantled this engine (pic 32).
• Push the clutch housing spacer onto the end of the mainshaft (pic 33), followed by the clutch outer housing, making sure the teeth engage correctly with the teeth on the electronic ignition flywheel (pic 34).
• The clutch inner housing is pushed into position on the mainshaft (pic 35), followed by its tab washer and retaining nut.
• Lock the clutch inner (using the same method used in the disassembly process), tighten the retaining nut (pic 36) and knock back the tab washer.
• Now replace the clutch plates; friction plate first followed by the plain plate with angled locating pins (pic 37). This plate should be fitted so the angled pins face outwards. Now fit the rest of the plates, alternating friction and plain.
• Fit the clutch activating plate making sure the holes allow access to the clutch spring retainers (pic 38).
• The clutch spring buckets (pic 39) can now be pushed into place followed by the Allen screws and washers (pic 40). Tighten the Allen screws in diagonal sequence so the plates house properly.

That’s the bottom end finished. The heads are reshimed by reversing the dismantling process, already covered in a previous issue. All that remains is fitting the top end, which we'll do next month.