Machining cylinder bores in upper crankcase section

The upper crankcase section is an aluminium alloy product and contains minute particles of pure sili-cium.

In order to have an usable cylinder surface finish, the cylinder bores have to be machined in a manner that the silicium particles protrude out of the aluminium and therefore pistons and piston rings only have contact with the silicium.

If it is necessary to machine cylinder bores, they can be restored with a SUNNEN CK-10 / CV - 616 cylinder repairing machine for installation of oversize pistons.

Standard size 100.00 mm

Oversize 1 100.50 mm

Single cylinder bores can be machined as required, since pertinent oversize pistons weigh the same as standard pistons.

Prior to machining cylinder bores it is recommended to check the stocks on hand for pertinent tolerance groups and, if necessary, to hone the bore for a certain piston size which is available. There could be problems in supplying pistons of certain tolerance groups depending on circumstances.

The following procedures are necessary:

Rough turning to 0.1 mm before finished size. Dressing to 0.02 mm before finished size. Polishing to finished size. Lapping with Sunnen silicium mixture.

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