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Thread: Potential Group Purchase - Wiseco GS650 741cc pistons

  1. #391
    Join Date
    Aug 2012
    Location
    Columbus, Ohio
    Posts
    2,557

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    If you want to build more compression by not losing it with head gasket bore volume (thicker head gasket, gasket bore is larger than our 65mm cylinder bore), then it **might** be a better idea to run a 1.3mm head gasket and add .3mm to the base gasket thickness.
    That would give you the same quench height as stock OEM base + 1.6mm ordered / 1.5mm compressed head gasket.

    I am really needing to get this Wiseco 610cc GS550 rebuilt and out of my shop space so I can tear into the 77 550 donor engine and measure my deck height!!! Almost there... I want to get the block skimmed more than .003" just in case, which is about all I'd skim yours Andy if you order the 1.6mm head gasket.

    .1mm head gasket thickness additional means .1mm or about .004" to skim off the block if mine is the same as Andy's block height and installed deck height.
    So If those were my measurements, I'd go 1.7mm (stock base gasket or equivalent head gasket using .8mm base) so that I could have .040" quench distance and be able to mill .007" off the top of the block deck if necessary.

    Thoughts????

    '77 GS750 920cc 4-1, 18" Sun rims, GS1100E swinger, susp.& brake mods
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported + Wiseco piston, susp. mods
    '76 Rickman CR GS1000-1105cc roadracer Yoshi cams& pipe, 89 GSXR1100K fork, 310mm discs, Fox Shox
    '79 GS425 489cc, megacycle cams, GS500 fork Fox Shox 310mm disc, DID rims, GS1100E swinger,
    '77 GS550's - 650-740cc susp/brake mods

  2. #392
    Join Date
    Aug 2015
    Location
    Fargo, North Dakota
    Posts
    122

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    How doesn't surfacing the head affect squish band? If you take material off the surface of the head it will move the pistons closer to the head chamber. How is it different than surfacing the cylinders?

  3. #393
    Join Date
    Aug 2012
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    Columbus, Ohio
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    2,557

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    Quote Originally Posted by Ace07 View Post
    How doesn't surfacing the head affect squish band? If you take material off the surface of the head it will move the pistons closer to the head chamber. How is it different than surfacing the cylinders?
    Because the squish band is the distance between the flat surface of the head just outside of the combustion chamber to the flat surface on the edge of the piston's top, next to the dome. if you were to look at the 650 head after you removed it, you would see carbon or some other markings that show you that the head gasket bore is much larger than the combustion chamber (especially on a closed chamber heads such as the 650), and if you measure the combustion chamber, it is substantially smaller than the bore of the piston. The squish band is the distance between the two flat surfaces at top dead center.

    some older bikes and models like the gs550 do not have a quench area to measure the squish band from, the 550 piston is 100% dome, no flat area on the top, & the combustion chamber mirrors that. a lot of older Hondas are like this from what I gather. The quench design is more efficient than the full hemi bore / full sized chamber.

    the only thing that surfacing the head affects like I said is piston to valve clearance, & cam timing (the chain is shorter distance between the crank and cams). And compression ratio of course.

    on major head resurfacing, if you had high domed high-compression pistons, you would need to be concerned about the piston dome contacting the chamber.
    Last edited by Chuck78; 06-16-2017 at 06:13 AM.

    '77 GS750 920cc 4-1, 18" Sun rims, GS1100E swinger, susp.& brake mods
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported + Wiseco piston, susp. mods
    '76 Rickman CR GS1000-1105cc roadracer Yoshi cams& pipe, 89 GSXR1100K fork, 310mm discs, Fox Shox
    '79 GS425 489cc, megacycle cams, GS500 fork Fox Shox 310mm disc, DID rims, GS1100E swinger,
    '77 GS550's - 650-740cc susp/brake mods

  4. #394
    Join Date
    Aug 2015
    Location
    Fargo, North Dakota
    Posts
    122

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    How close are we to ordering these gaskets?

  5. #395
    Join Date
    Aug 2012
    Location
    Columbus, Ohio
    Posts
    2,557

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    so far we've only got two deck height measurements, I should be finished with this bike I'm working on tomorrow and can pull out the 550 engine and measure my own deck height after dismantling & clearancing the case
    I've been meaning to compare your deck height measurements to Suzuki Don's:
    Posts 132 through 150ish+
    http://www.thegsresources.com/_forum...d-Rattle/page4

    Wife is mostly around the Midwest next 8 weeks so I'll be getting more pressure from her to get her "superbike" (the 1st of 2 550 builds here) done... I will definitely be needing these gaskets soon!

    Doesn't appear that anyone else has as much priority placed on it as you and I Andy, but sheesh I'm sitting in a garage now filled with 9 bikes & 6 spare GS engines, 2 Rickman bikes in basement, 2 more GS engines and 2 do are Suzuki 250 Enduro engines... lots to keep me busy here!!! 1 more bike coming in for service from a friend, too! May as well put up a mailbox at the garage door!

    '77 GS750 920cc 4-1, 18" Sun rims, GS1100E swinger, susp.& brake mods
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported + Wiseco piston, susp. mods
    '76 Rickman CR GS1000-1105cc roadracer Yoshi cams& pipe, 89 GSXR1100K fork, 310mm discs, Fox Shox
    '79 GS425 489cc, megacycle cams, GS500 fork Fox Shox 310mm disc, DID rims, GS1100E swinger,
    '77 GS550's - 650-740cc susp/brake mods

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