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Thread: Machine Shop Question

  1. #11
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    Jay from APE has cautioned here before about milling the head to correct flatness issues because that may in part create cam binding issues. The reasoning being that when Suzuki built the head the cam bores were made parallel to the deck surface. If the deck is warped so are the cam bores. Thing is, when tightening the head nuts that flattens the head and straightens it...but not if the head is milled to correct flatness issues. As I recalled he advocated bending the head to straighten it. My memory isn't the best though. Bottom line, I'd be careful about milling the head unless it's just a light clean up cut.

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    Measuring the bores to see whether there is any 'out of roundness'/egg-shaped wear is highly recommended:I don't own an inside micrometer..
    I had used a 3-stone spring loaded hone and done a quick glaze-braking in the past on many cylinders and installed new rings.A few of those engines started using oil even with new rings.A bore job is more expensive but if there is elliptical/out-of-round wear in the bores,this will give you back a fully round bore and the rings will break-in nice and you'll have plenty of excellent,consistent compression/ring sealing:the rebuild will last a long time. I would love to have a shop with machinist tools including a precision 4-stone hone such as an expensive Sunnen.. for now I live in a cheap apartment so I bring my parts to a professional machinist and pay the $.
    Last edited by grcamna2; 01-28-2021 at 01:05 AM.

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    If you are going to a machine shop anyway with your head, try using their surface plate to check flatness. This is a slab of granite ground absolutely flat and is a reference tool for checking flatness. Every machine shop has one.
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    Quote Originally Posted by bwringer View Post
    Also, depending on which version of the OEM head gasket you end up with (do not even consider aftermarket), you may not need that square o-ring around the center tunnel. Later versions just cover this area with gasket; earlier versions were open here so the o-ring formed the seal.
    Excellent information bwringer. Thanks very much.
    Oh, and I have every intention of using OEM gaskets and such
    Last edited by RustyTank; 01-28-2021 at 10:04 AM.
    1979 GS850G, currently being rebuilt from the frame up. We shall see how that go's

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    Quote Originally Posted by Nessism View Post
    Jay from APE has cautioned here before about milling the head to correct flatness issues because that may in part create cam binding issues. The reasoning being that when Suzuki built the head the cam bores were made parallel to the deck surface. If the deck is warped so are the cam bores. Thing is, when tightening the head nuts that flattens the head and straightens it...but not if the head is milled to correct flatness issues. As I recalled he advocated bending the head to straighten it. My memory isn't the best though. Bottom line, I'd be careful about milling the head unless it's just a light clean up cut.
    Ok. It sounds like the best thing to do is, once I get the left over gasket gunk off, just check flatness, if it's good, go with it.
    Thanks a lot Nessism.

    Quote Originally Posted by zuluwiz View Post
    If you are going to a machine shop anyway with your head, try using their surface plate to check flatness. This is a slab of granite ground absolutely flat and is a reference tool for checking flatness. Every machine shop has one.
    That's a great idea! Thanks zuluwiz
    1979 GS850G, currently being rebuilt from the frame up. We shall see how that go's

    "The two most powerful warriors are patience and time" - Leo Tolstoy

    " Be yourself, everyone else is already taken" - Oscar Wilde

    "Do things for people not because of who they are or what they do in return, but because of who you are" - Harold S. Kushner

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    Quote Originally Posted by grcamna2 View Post
    Measuring the bores to see whether there is any 'out of roundness'/egg-shaped wear is highly recommended:I don't own an inside micrometer..
    I had used a 3-stone spring loaded hone and done a quick glaze-braking in the past on many cylinders and installed new rings.A few of those engines started using oil even with new rings.A bore job is more expensive but if there is elliptical/out-of-round wear in the bores,this will give you back a fully round bore and the rings will break-in nice and you'll have plenty of excellent,consistent compression/ring sealing:the rebuild will last a long time. I would love to have a shop with machinist tools including a precision 4-stone hone such as an expensive Sunnen.. for now I live in a cheap apartment so I bring my parts to a professional machinist and pay the $.
    A bore gauge is needed to check cylinder wear. An inside mic could possibly be used but it's not the right tool for the job. And when deglazing cylinders a ball hone is much better than a straight hone like you mention. With a straight hone any slight out of round or taper will result in missed spots in the cylinder where the hone is inconsistent.

    Checking the cylinder head for flatness on a surface plate is not ideal because you will only be able to check the very outside edges. Honestly though, we are really splitting hairs in this thread. Just use a half way decent ruler and look for large inconsistencies in flatness. 95% chance it's fine. I'd be more concern with valve guide and valve/seat wear.

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    Quote Originally Posted by Nessism View Post
    A bore gauge is needed to check cylinder wear. An inside mic could possibly be used but it's not the right tool for the job. And when deglazing cylinders a ball hone is much better than a straight hone like you mention. With a straight hone any slight out of round or taper will result in missed spots in the cylinder where the hone is inconsistent.
    I need to pick up a bore gauge to check cylinder wear. If anyone has a particular brand they like let me know, maybe they're all the same though.


    Quote Originally Posted by Nessism View Post
    Checking the cylinder head for flatness on a surface plate is not ideal because you will only be able to check the very outside edges. Honestly though, we are really splitting hairs in this thread. Just use a half way decent ruler and look for large inconsistencies in flatness. 95% chance it's fine. I'd be more concern with valve guide and valve/seat wear.
    Great note about priorities "I'd be more concern with valve guide and valve/seat wear". Thanks Nessism.
    1979 GS850G, currently being rebuilt from the frame up. We shall see how that go's

    "The two most powerful warriors are patience and time" - Leo Tolstoy

    " Be yourself, everyone else is already taken" - Oscar Wilde

    "Do things for people not because of who they are or what they do in return, but because of who you are" - Harold S. Kushner

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    [QUOTE=RustyTank;2639602]I need to pick up a bore gauge to check cylinder wear. If anyone has a particular brand they like let me know, maybe they're all the same though..../QUOTE]


    Starrett or mitutoyo, but they are spendy
    There are lots of cheap bore gauges on amazon.
    ... unless you're running a rebuild shop I don't see the need.

    You can get a "good enough" read on bore wear using a piston and a feeler gauge.
    It won't tell you the actual diameter but it will indicate wear.

    A lot of talk about head gaskets and flatness... and no one has mentioned Cometic copper gaskets.
    The GS has head sealing problems, copper gasket is an answer.
    Better head studs help too.

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    Quote Originally Posted by RustyTank View Post
    I need to pick up a bore gauge to check cylinder wear. If anyone has a particular brand they like let me know, maybe they're all the same though..../QUOTE]


    Starrett or mitutoyo, but they are spendy
    There are lots of cheap bore gauges on amazon.
    ... unless you're running a rebuild shop I don't see the need.

    You can get a "good enough" read on bore wear using a piston and a feeler gauge.
    It won't tell you the actual diameter but it will indicate wear.
    Thanks for your two cents bitzz. I looked them up and wow, those brands you mentioned are indeed expensive. I guess I'm just curious if one of the cheaper bore gauges is going to be even worth my time/money, but I hear what your saying.


    Quote Originally Posted by bitzz View Post
    A lot of talk about head gaskets and flatness... and no one has mentioned Cometic copper gaskets.
    The GS has head sealing problems, copper gasket is an answer.
    Better head studs help too.
    I went to Cometic's website and found an 80 and 81 GS850 copper head gasket, but not a 79. Mine is a 79. It may not make a difference, I don't know the 80/81 engines well enough to know.
    1979 GS850G, currently being rebuilt from the frame up. We shall see how that go's

    "The two most powerful warriors are patience and time" - Leo Tolstoy

    " Be yourself, everyone else is already taken" - Oscar Wilde

    "Do things for people not because of who they are or what they do in return, but because of who you are" - Harold S. Kushner

  10. #20
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    Do NOT get a copper gasket if you care about oil tightness. Copper is for race engines where a little weepage is acceptable.

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