How to Hone a Motorcycle Cylinder
Motorcycle cylinder honing is as much art as it is science. Subtle variations of the standard honing technique allow the mechanic to remove material from the cylinder bore to straighten or "true" the bore as well as correcting minor out-of-round conditions. Rigid hones with three or four stones mounted on articulated fingers perform the material removal operations. Ball hones, or "flex hones," are used to put the final crosshatch pattern on the cylinder walls. This crosshatch helps retain lubricating oil on the cylinder wall to prevent piston galling and aids in new piston ring break-in.
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Things You'll Need
- Torque plates
- Socket set
- 3/8-inch ratchet
- Bench vise
- Shop rags
- Micrometer set
- T-gauges or dial-bore indicator
- Drill motor
- Rigid cylinder hone
- Ball (flex) hone
- Honing oil
Instructions
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1
Position the cylinder between the torque plates. Torque the plate bolts to compress the cylinder according to factory specifications. Wipe all oil from the inside of the cylinder. Clamp the bottom torque plate in the bench vise at the plate's clamp tab.
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2
Measure the cylinder with the T-gauges or dial-bore indicator and the micrometer. Make a series of six measurements. Measure the top, middle and bottom of the cylinder on both the X and Y axes. These measurements will reflect the straightness and roundness of the cylinder bore.
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3
Chuck the rigid hone up in the drill motor. Release the hone adjuster to collapse the hone. Clean the stones with a rag then lightly oil the stones. Tighten the hone adjuster until light drag is felt between the hone and the bore. Insert the hone into the cylinder bore. Squirt some honing oil onto the cylinder walls between the stones.
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4
Operate the drill motor and bring the RPMs up to medium speed. Move the hone up and down in the cylinder. Plunge and retrieve the hone only enough so that the ends of the stones barely clear the end of the cylinder. Do not allow the stones to fully clear the end of the bore, or cylinder bore and hone damage will occur.
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5
Move the hone up and down in the cylinder with a steady motion. Insure that the resulting scratches in the cylinder walls that will form the crosshatch pattern intersect each other at a 60 degree angle. Modify your drill speed and movement speed until this is achieved. Pause slightly in your hone movement, without stopping rotation, in the areas revealed to be smaller in diameter by your measurements. Modifying the travel allows you to make the minute adjustments needed to true and round the bore. Oil the cylinder frequently during this process with honing oil to prevent the cylinder from heating up or drying out.
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6
Withdraw the hone completely and measure the cylinder to check on your progress. Start with the flex-hone once the cylinder measures true and round. Chuck up the flex-hone and insert it into the bore. Squirt some honing oil into the bore and rotate the hone at medium speed. Move the flex-hone up and down in the cylinder with the same motion as the rigid hone to achieve the 60 degree crosshatch. Continue this motion until a nice, consistent crosshatch pattern is established. Remove the hone and wipe the cylinder walls well with a clean shop rag to remove any metal, salt or stone fragments. Remove the torque plates from the cylinder.
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Tips & Warnings
Use feel and sound to determine when the cylinder is getting close to the right shape. Tight areas will give more resistance to the hone rotation and sound different than loose areas. Pause your in and out travel slightly at the tight areas to remove excess material and loosen these spots up.
As material is being removed from the cylinder walls, it will be necessary to adjust the hone to progressively larger sizes to maintain the proper stone-to-bore pressure.
Do not push or pull the rigid hone too far during operation. Allowing more that 1/4 of the length of the hone to overlap the ends of the bore can cause the hone to bind, which can damage the cylinder, destroy the stones and cause bodily injury as the drill motor tries to rotate itself since the hone cannot rotate.
