How to Rebuild a GL1100 Engine

Written by troy lambert
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How to Rebuild a GL1100 Engine
Replace damaged pistons during a rebuild. (piston de scooter image by Vetea TOOMARU from

Rebuilding a Honda GL1100 motor requires a great deal of mechanical ability and knowledge. Reassembly requires a great deal of concentration and some speciality tools. When timing is set, it must be done exactly, as the 1100 is an interference motor. Engine damage will result if you do things incorrectly. Have a motor manual handy and your rebuild can be successful.

Skill level:

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Things you need

  • Reference manual
  • Engine stand
  • Metric sockets and wrenches
  • Feeler gauge
  • Piston pin tool
  • Micrometer
  • Straight edge or glass plate
  • Inside micrometer
  • Cylinder hone
  • Plastigauge
  • Dial indicator
  • Piston ring compressor
  • Torque wrench

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  1. 1

    Drain oil and coolant from the motor and discard. Place the motorcycle on its centre stand and remove the engine from the frame. Place it securely on an engine stand. The engine is heavy, so you will probably need an assistant for this step in the process.

  2. 2

    Disassemble the engine case, starting at the rear of the engine. Remove the vacuum advance mechanism, the mechanical advancer, and the rear engine cover. Remove the scavenge pump bolt and sprocket and the mechanical advancer driveshaft. Remove the starter as well. Label all parts and bolts as you remove them and place them on a large clean work area.

  3. 3

    Remove the coolant tubes, the cylinder head covers and the timing belt covers. Turn the motor to top dead centre (TDC) and mark each timing belt with an arrow to show direction of rotation. Also mark the belts with a R and an L to indicate which side they came from. Loosen the belt tensioner bolts, and move them away from the belts, then retighten the bolts. Remove the belts, using caution not to get oil on the belts or they will need to be replaced. Rotate the crankshaft 90 degrees either direction from top dead centre. This will allow you to move the camshafts without driving a valve into the piston.

  4. 4

    Remove the front engine cover, the camshaft pulleys and the camshafts. Remove the cylinder heads, and set aside. Remove the 19 bolts from the left engine case, and the three bolts from the right. Rotate the engine so the left side is up. Move the shift arm away from the shift drum, and partially separate the case halves. Use a couple of two by fours to support the upper case, and place shop towels under the pistons, so they will not strike the transmission when the left case is removed. Lift off the left engine case.

  5. 5

    Remove the left and right side rods and pistons, using a metal marker to mark which cylinder they came from. Remove the crankshaft, and carefully set it aside.

  1. 1

    Inspect the rods, pistons and crankshaft for wear. Replace any items that do not pass inspection. Using the inside micrometer, inspect the cylinders for out of round and wear. If cylinders are worn, and it is necessary to bore them, purchase new pistons to fit the new bore. Inspect the cylinders for warpage, checking in a criss-cross pattern. If cylinders do not need to be bored, deglaze them using a cylinder hone.

  2. 2

    Use a dial indicator to check the crankshaft for taper and out-of-round. Temporarily reinstall the crankshaft, and use plastigauge to determine if bearings need to be replaced. If they do, consult the manual for bearing selection, and purchase new bearings. Using a piston, push a piston ring into the cylinder. Inspect the end gap, and if it does not fall within service limits, replace the piston rings.

  3. 3

    Clean all parts thoroughly if they are to be reused. As new items are placed on the work surface, throw away old items, or set them aside elsewhere so that they are not accidentally reused. Lay out all tools you will need, and ensure that they are clean before beginning reassembly.

  4. 4

    Install the crankshaft. Stagger piston ring gaps 120 degrees apart. Coat pistons and rings with a thin coat of oil before reinstalling. Install the right side pistons and rods in the cylinders they came out of, using the piston ring compressor. To prevent damage to the crankshaft, place small sections of rubber hose over the rod bolts before installation. Install rod caps, and torque to specification. Install left side pistons and rods, ensuring the rods face the proper direction and oil holes line up. Reinstall the left engine case, using the case support and piston bases. Apply sealant to the case halves, remove the piston bases and case supports, and seat the cases together. Tighten bolts to correct torque specifications.

  5. 5

    Continue reassembly in the reverse order of disassembly. Using the torque wrench, torque all bolts to the proper specification. Use new gaskets and o-rings to ensure there are no leaks. Follow all steps in the manual regarding timing belt installation, as improper timing will cause severe engine damage. Reinstall the engine in the frame. Run the engine, and inspect for leaks.

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