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Thread: 750/850 hybrid pistons search

  1. #11
    Join Date
    Aug 2012
    Location
    Columbus, Ohio
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    3,601

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    And if you search the Honda CB forums, you will find lots of long-term reviews of those pistons in the CB big bore variety.

    This GS650 big bore kit however is a completely different issue, very careless and irresponsible on their part to sell such a thing that won't even fit the head, they probably never tested it or had a head in hand or any data on what the combustion chamber shape or size was.

    '77 GS750
    920cc, 4-1, GS1100E swinger, 18"rims, Fox Factory Shox, twinpot dual disc, VM29's, Yoshi cams
    '99 Kawasaki KDX220 rugged terrain ripper
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 Pure Enduro trail beast, ported, Wiseco, TüBliss, Fox Factory Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yoshi cams&4-1, RF900R fork, Works ProRacers
    '79 GS425 489cc, GR650 cams, GS650 fork, twinpot discs, DID rims, GS1100E swinger, Fox Factory Shox
    '77 GS550 650-740cc susp/brake mods

  2. #12
    Join Date
    Aug 2012
    Location
    Columbus, Ohio
    Posts
    3,601

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    A member named Ian / 49er custom designed a set of 71mm stock compression ratio pistons several years ago & had JE Pistons manufacture them for him. I think he also did a big big bore setup as well, but didn't really end up doing a lot with that engine as he was very pleased with the 890-ish cc (894cc?) incarnation if my memory serves me correctly. I discussed these engines with him at great length. I'm sure you could have JE Pistons, Carillo/CP, or other manufacturers make the same for you if you sent them a mold of the combustion chamber and a stock piston

    '77 GS750
    920cc, 4-1, GS1100E swinger, 18"rims, Fox Factory Shox, twinpot dual disc, VM29's, Yoshi cams
    '99 Kawasaki KDX220 rugged terrain ripper
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 Pure Enduro trail beast, ported, Wiseco, TüBliss, Fox Factory Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yoshi cams&4-1, RF900R fork, Works ProRacers
    '79 GS425 489cc, GR650 cams, GS650 fork, twinpot discs, DID rims, GS1100E swinger, Fox Factory Shox
    '77 GS550 650-740cc susp/brake mods

  3. #13
    Join Date
    Sep 2015
    Location
    Amsterdam
    Posts
    55

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    I did not know they made reliable Honda pistons (i never look at their forum )
    For me this is a challenge building a block from the ground up.
    And this is the first time i am looking for upgraded pistons.
    The idea of forged pistons and higher compression seems nice for tuning..
    The different carburation, clearences etc will test my knowledge and the server from gsresources
    But making moulds of the combustion chamber, sending them to the USA and order custom pistons seems too complicated for my ´project´
    If there would be pistons available off the shelf i would go for it.
    Since the Wiseco set has good reviews with the 70 block i think i better let go of the 850 cilinder block and focus on the CV 850 head and the 28mm carbs.
    But thanks for the input !!!
    Under no circumstances should both hands be removed from handlebars.
    (1977 owners manual)

  4. #14
    Join Date
    Aug 2012
    Location
    Columbus, Ohio
    Posts
    3,601

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    Also, if you wanted 71mm GS850 big bore pistons for 900cc (894cc actually?), if you found 2 other interested buyers with 750's + 850 cylinders, or just a GS850, Wiseco would make you a minimum batch of 12 custom pistons (3 sets) for about the standard price, and you'd be able to use the Multi-Layer Steel (MLS) GS1100G OEM head gasket. They'd be able to pretty easily re-draw their K844 piston fpr larger bore and smaller dome to have these CNC manufactured. They could easily do 72mm as I have as well,for 920cc even.

    Just food for thought.
    You'd be happy with stock 850 piatons honestly, but biggercams and higher compression of the Wisecos is even better,especially if it's 50cc or 76cc larger displacement!

    '77 GS750
    920cc, 4-1, GS1100E swinger, 18"rims, Fox Factory Shox, twinpot dual disc, VM29's, Yoshi cams
    '99 Kawasaki KDX220 rugged terrain ripper
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 Pure Enduro trail beast, ported, Wiseco, TüBliss, Fox Factory Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yoshi cams&4-1, RF900R fork, Works ProRacers
    '79 GS425 489cc, GR650 cams, GS650 fork, twinpot discs, DID rims, GS1100E swinger, Fox Factory Shox
    '77 GS550 650-740cc susp/brake mods

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