Measuring cylinder bore, taper, and out-of-round

[noli]

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Hi,

Though I'd share this great video on how to measure the cylinder bore and taper when rebuilding outboard motors












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[noli]

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[noli]

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What do these numbers mean when purchasing a rebuild kit for your motor

[nitro_rat]

Measuring the bore prior to a rebuild will give the machinist an idea of how much material will have to be removed to "clean up" the cylinder. This is how you know what size pistons to order (.015, .030, .060, etc). Due to manufacturing tolerances the actual pistons you are going to use should be measured before final honing is done.

[2jz]

Standard bore on optimax is 3.625 on a perfect cylinder bore

Depending on cylinder condition or problem. Ex out of round, normal wear,or scratches because of bad piston. That cylinder has to bored back to perfect which includes removing material from cylinder bore. Once this is done your standard piston can't b used you have to go oversize..015 or .030 depending how much material was removed. So 3.625 plus .015 or .030 is your new bore diameter.
Rule of thumb for a none Machinist just looking at cylinder bore with scratches if ur finger nail gets hung on small scratches cylinder needs over bore