2003 Ducati ST4s Timing Belt Adjustment

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Filed Under (Aprilia) by admin on 31-10-2010

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This instruction on cam belt adjustment starts after you remove the fairing pieces. Plan on an hour to remove these. Since you are performing your own service, buying Ducati belts may not be that expensive. There may be another belt source, but I have not confirmed this for the 996 engine of the 02-03 ST4s. Fig 1 – ST4s ready for belt adj./ repl. Fig 2 – Crank tool installed. See dwg. 1) Ensure maximum of ½ tank of gas. Fuel will leak into the charcoal canister, then onto the floor if the tank is over half full and the tank is tilted up on its hinge. So put the tank up on its hinge. 2) Remove spark plugs. Cover sparkplug wells with boots or rags. This is a great time to toss out those Champions for a set of NGK DCPR8E’s. 3) Remove the front shield from the horizontal cylinder head. 4) Remove crankshaft cover on Riders LH side and insert crank tool. A crank tool can be made by following the drawing at the end of this document. See Fig 2 above. The flat head screws used are kind of soft so beware on their removal. 5) Remove oil pressure sending unit cable and remove oil sending unit. No oil should pour out. 6) Remove battery and remove bolts fastening battery box to engine/frame. You can let the battery box dangle or partially support it via a bungee cord. Be careful of the cable on the ground of the ECU. By dangling the battery box excess stress could be placed on this cables connector and you don’t want to troubleshoot an intermittent electrical issue. 7) Remove cam belt covers. The two covers over the cams are real easy. The center piece is removed by pulling it down. You may have to move some hoses and cables out Timing belt adj. doc 1
of the way because it is a tight fit. Removing the oil pressure sending unit gave clearance for the removal. Fig 1 shows bike ready to be worked on. On the Rider’s LH is a window on the case cover. Using a flashlight to illuminate the area, marks can be rotated into view using the engine turning tool. There are two marks denoting the TDC of each of the cylinders. When a mark in the window aligns with the pointer, look at the crank driving pulley on the Rider’s RH of the engine. If the driving pulley’s mark is aligned with the pointer on the engine case, you are at TDC horizontal cylinder. If the pulley mark and the pointer on the engine do not align, rotate the engine until the mark in the window on the Rider’s LH side case cover aligns as well as the pulley’s mark and the engine’s pointer. Fig 3 shows the engine pulley and pointer. You can check that the horizontal piston is at TDC by inserting a welding rod into the spark plug well and touch the top of the piston with it to sense its position. Timing marks on cam pulleys are clearly stamped on all four pulleys. When the crank driving pulley aligns with its corresponding pointer on the engine case and the marks on the pulleys align with their corresponding marks on both cylinders, you are in position for belt adjustment and replacement

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