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Thread: SP4 Rebuild

  1. #11
    Join Date
    Oct 2019
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    South East
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    SP4 - red injectors on display mainly due to deep, very slow clean :-)
    Attached Images

  2. #12
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    Jan 2014
    Location
    Northamptonshire
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    Quote Originally Posted by stiglarsenDK View Post
    Did the sp4 come w red injectors ??

    This set is NOS, thought it was from earlier sp version or even kit
    As far as I'm aware the injectors on this bike are standard but I do have a set of greens cleaned and ready to go if necessary.

  3. #13
    Join Date
    Jan 2014
    Location
    Northamptonshire
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    126

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    Heads before during and in progress.

    Chambers looked OK upon disassembly so quick clean up with a dremel and brass wire brush. They were then vapour blasted by Andy at Northants Vapour Blasting.

    Exhaust valve guides were worn so out with the old and a clean up of the ports to match the Sil Moto header flanges.

    Oversize valves from Fast by Ferracci then off to Simon at Northampton Automotive Services for guide fitting, new inlet seats and 3 angle seat cutting.

    First cut on the sets just to clean ready for a quick dry build to check shim clearances.
    As you can see first cut was consistent as the same depth of cut required on seats in both heads to put the valves at the optimum depth.

    Once finish cut, ports will be fettled to blend new seats then chambers will be further optimised before volume measurements. Then skim or not to skim....
    Attached Images
    Last edited by tubbylad; 01-14-2021 at 06:03 AM.

  4. #14
    Join Date
    Nov 2007
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    Augustinusga, the netherlands
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    Looking great!

    Still using the OEM valves, so 33/29 mm?
    Nice to see that the valve guides were shortened for optimized airflow in the ports.
    Thatís what has been done to my heads as well by vd Biggelaar (Ducati tuner in The Netherlands).

    And the sil moto exhaust, is that the spaghetti one?

    Regards,
    Jacco

  5. #15
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    Jan 2014
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    Northamptonshire
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    Quote Originally Posted by jakepeewee View Post
    Looking great!

    Still using the OEM valves, so 33/29 mm?
    Nice to see that the valve guides were shortened for optimized airflow in the ports.
    Thatís what has been done to my heads as well by vd Biggelaar (Ducati tuner in The Netherlands).

    And the sil moto exhaust, is that the spaghetti one?

    Regards,
    Jacco
    Thanks Jacco.
    The valves are oversize at 37mm and 31mm.
    Image of the Sil Moto headers attached.
    Attached Images

  6. #16
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    Nov 2007
    Location
    Augustinusga, the netherlands
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    Quote Originally Posted by tubbylad View Post
    Thanks Jacco.
    The valves are oversize at 37mm and 31mm.
    Image of the Sil Moto headers attached.
    I bought the same Sil Moto headers, curious to find out how they will work on my bike (SP3).
    There's not a lof of info on the effect of these tangential headers, especially compared to the better flowing 50mm X headers we already have on our bikes.

    That's a really interesting tune you're doing to your bike with the 37/31.
    What cams will you be using? The OEM SP4 pistons are designed for the old architecture camshafts, so deep valve pockets. Makes it harder to get a CR of 12+

  7. #17
    Join Date
    Dec 2018
    Location
    Australia
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    106

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    I have those headers on my ST4 engined unit and I can say that I also have no data on how well they work, other than each cylinder pulse feels perfectly equal, and it sounds amazing.
    Put them on, you won't be disappointed.

  8. #18
    Join Date
    Nov 2007
    Location
    Augustinusga, the netherlands
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    170

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    Quote Originally Posted by econti View Post
    I have those headers on my ST4 engined unit and I can say that I also have no data on how well they work, other than each cylinder pulse feels perfectly equal, and it sounds amazing.
    Put them on, you won't be disappointed.
    Thanks for your first hands experience, appreciated.

  9. #19
    Join Date
    Jan 2014
    Location
    Northamptonshire
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    Valves now cut to depth with 3 angle seats. Works manual page shows what we're working towards.

    So a few pictures showing the work in progress on the heads.

    Clearly some room for improvement blending in new inlet seats.
    Maybe a bit of unshrouding work too to help flow the larger valves.

    Inlet port view is pretty much as the head came from factory.

    Exhaust ports have been opened up to closer match the Sil Moto header flanges.
    Attached Images

  10. #20
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    Jan 2014
    Location
    Northamptonshire
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    126

    Default Radiator Goodness

    Don't think we'll be having any cooling problems.
    Quality exudes throughout.
    Attached Images

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