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  1. #1
    CB750 New Member BAMotobuild's Avatar
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    Jul 2019
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    Illinois
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    4

    Sanding the head?

    Getting ready to put the engine of an 82 SC back together and I want to bring the head surface to a good finish. There is for sure some surface rust from the original gasket left over onto the aluminum. what would be the best way to get this cleaned up nice? I plan on using gaskets from here unless you recommend a better one.

    I have a very flat machinist measuring stone i planed on sanding the heads with, but which grit of sand paper should I finish with? Alternatively, is there a better less invasive method? From what i can tell currently, i have about .002"-.003" of difference across the head but is may not have it as cleaned and as flush as it can be.

    Thanks for the help.

    If interested, you can follow along the build below!
    https://www.youtube.com/channel/UCAX...IM-yilnFzyGAug

  2. #2
    CB750 Guru amc49's Avatar
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    Sep 2015
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    Fort Worth TX.
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    2,437
    Don't think you are going to even that up, it would take a week and then the flats would be worse.

    No machinist ever measures using a stone, it is for honing knife blades and such. Machinists if anything use a block of solid machined metal to gauge with. A stone is not reliable enough to sand with on a machined flat unless it is trued just before using it. Any use quickly removes that property too.

    I use 400 sandpaper by hand in small pieces easily controlled, it works fine. You may have impressions from the fire rings around the cylinder holes, leave them alone rather than try to even them out, it will blow head gasket faster if you level the impressions out to zero. Just dust them along with the rest of the flats. You DO need to remove any slight highs like screwdriver pry marks, let the lows go, lows don't hurt and actually seal better.

    Anal retentive but it works beautifully, use a razor blade leaned way over to not gouge to clean the last bit that does not come up with major old gasket and then chase with the 400 sandpaper, nothing better on earth there.

    All complicated aluminum castings that get heat like engines warp here and there when used, they bolt back up fine and seal perfectly if you just do basic rules like torquing to spec in small steps, it allows the flats to equalize more. GOOD cleanup is a must as well.

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