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Thread: 750 cams in a 1000?

  1. #11
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    Jul 2009
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    Quote Originally Posted by salty_monk View Post
    I guess in a restricted race series where you are trying to legally ring every fraction of a HP it might have been a mod to use....
    Here, for production racing, what you did was get Suzuki NZ to build - and homologate as production - a run of bikes with Yosh Stage 2 cams, the 30mm carbs and big bore pipes.
    There is of course a long existing controversy as to how many were built. They are also changing hands for ridiculous money.

    I've said before on 750 cams, it's not what model cam you have in the motor, it's the timing you use that makes the difference.

  2. #12
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    Aug 2012
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    I have ran both 750 and 850 cams in various incarnations of my GS750 big bore bike... The 850 cams should be the same as the 1000 cams, but the cam sprockets may or may not be different timings.
    And also I believe the lift is not the same between the 750 and 1000/850 cams, I believe the 1000 has slightly more lift, whereas the 750 has slightly more duration.

    As far as the difference in similar engines, I definitely noticed more mid-range grunt with the 850 cams and 850 cylinders that I am running now on my 750. I have ran the 750 cams on both a 750cc setup, as well as 850cc and 920cc.
    The 750 cams with their additional duration absolutely have more high-end horsepower, plenty enough additional to notice, but the 850/1000 cams are definitely more fun in this displacement range on the street without having to rev it to the moon and alert everyone within 3 miles of ludicrous riding style wringing the *@%^$* out of your engine!

    The added mid-range grunt was absolutely noticeable on the swap to 850 cams, but the lack of that extreme acceleration at the top of the tach was definitely noticeable now that I'm not running the 750 cams. On an 844cc engine with a 4-1 Delkevic exhaust and K&N RC-2222 air filters, both camshafts were very fast, but both had different characteristics that were noticable.

    I think that in a 1000 cc engine having more torque by default due to the displacement, the 750 cams would be plenty fun on the street and for when you really can rev it to the moon. Although the cam tensioner set up on the head on the 1000 is not as happy to rev much above redline, unlike the GS750 and GS850 cam tensioner set up, with the additional idler wheel in between the cams. Running a heavier duty aftermarket cam chain for the 1000 per rapid ray's recommendation will alleviate most troubles you would have with wearing out the cam chain on the 1000 from revving it too high.
    Pops Yoshimura actually modified the 1000 heads to run the 750 cam chain setup with a custom length chain I believe! That alleviated their endurance race troubles with the cam chain setup.
    Last edited by Chuck78; 05-26-2021 at 03:00 PM.

    '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
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    Quote Originally Posted by Chuck78 View Post
    Pops Yoshimura actually modified the 1000 heads to run the 750 cam chain setup with a custom length chain I believe! That alleviated their endurance race troubles with the cam chain setup.
    He did, but it was not sturdy enough. Using the KZ1000 roller was the solution.
    At least that's what John Ulrich stated in his description of the Yoshi GS1000 mods.
    Can't find that article now though ...

  4. #14
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    Jul 2009
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    Quote Originally Posted by Rijko View Post
    He did, but it was not sturdy enough. Using the KZ1000 roller was the solution.
    At least that's what John Ulrich stated in his description of the Yoshi GS1000 mods.
    Can't find that article now though ...
    And it's not correct now anyway. Better camchain, cams and springs have made the standard tensioner blade work.
    They put in the center sprocket to get more chain wraparound on the cams. The springs they used made this neccessary.
    There are roadrace GS1000's here running more lift than Yosh did without the extras they used - with no problems.

    Time does not stand still. Better parts are available than they had then.

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