SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
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    KNOXVILLE TENNESSEE
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    Bryan,
    Received my new SBT engine today. A full week ahead of delivery schedule ! I thank your collegues in the shop for working so hard to "make it happen" !
    Unfortunately, I am still waiting on another vendor for support parts so I am in no rush to install yet.

    My question today is this:::::
    I was going over the RV timing instructions in the OEM manual as well as the SBT installation guide. (Your guide is much more explicite)

    Both installation instructions refer to the 1996 HX 720 engine with a RV opening of 147'. My particular unit came with a RV that has a 159' open duration. I matched the RV with the template in the OEM manual to verify as well as verification through SBT when I ordered a new one. If I go with the 147' spec.,,, the marks dont get very close, even if I flip the valve over.
    Surprisingly, if I go with the 159' duration and mark the cases accordingly it matches right up only when I flip it over to the opposite side of what it was originally installed(at the factory).
    The paint on the RV cover plate bolts do not indicate this cover has ever been R&R'd.

    Could the factory have installed this wrong ?
    I dont think this would have caused my front piston to fry but it seems awful strange. It always ran and idled smooth.

    Should I go with the 159' spec. and the closest match of my marks following the exact SBT instructions but substituting the 147' with my 159' ?

    David
    "On the Tennessee River"
    DAVID_HX_XP_RX-DI

  2. #2
    Joined
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    Clearwater, FL
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    You are confusing the duration of the valve (amount of open space on the valve) with the timing mark to set to. For your engine, you use a 159 deg. valve (size of the valve), and time it to 147 deg (where you set it on the case).

    There is a 147 duration valve, but it is for other applications and is just a coincidence that the numbers happen to match up - many people confuse these two things.

  3. #3
    Joined
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    Bryan,
    After reading the instructions again and taking a real good look at the photo I now see my mistake............ DUH !

    The LEADING EDGE of the RV is supposed to match with the 147' mark that was put on the case by moi. The bottom of the MAG intake port is just a zero reference as to where the 147' degree mark goes.
    I must have been dreaming about being on the water to miss this before !!!

    Now, I took this a step further; according to the OEM shop manual there is also a 65' (RV Closing) mark that is made in a similiar routine except instead of using the bottom of the MAG intake port as a zero reference,,you now use the top edge of that port and make a mark on the case edge at 65'.

    Then put the RV on the splined shaft to match those 147' and 65' marks as close as possible. (Trying both sides of the RV for the best match)

    My question is this................

    Is it better to be closest to the 147' mark with the leading edge of the RV or the 65' mark with the RV's trailing edge ??
    Or, since there is a +/- 5' tolerence does it really matter ?

    David
    DAVID_HX_XP_RX-DI

  4. #4
    Joined
    Feb 2001
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    Clearwater, FL
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    You slightly misread the instructions again. The 65 deg. mark is to be measured from the TOP of the intake port (you have to reposition the degree wheel), and at that point, both marks line up the same. You can time to either, as they are the exact same thing.

    I will be revising my instructions slightly for the next version, as I have had a few other calls from people that were confused as how exactly to time the valve...specifically, that you need to count back from the 0 deg. point and place the valve there, not move the degree wheel or set the valve to the port...

  5. #5
    Joined
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    KNOXVILLE TENNESSEE
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    Bryan, that is how I understood it now...........

    ~~~~previous comments~~~~~Now, I took this a step further; according to the OEM shop manual there is also a 65' (RV Closing) mark that is made in a similiar routine except instead of using the bottom of the MAG intake port as a zero reference,,you now use the TOP EDGE of that port and make a mark on the case edge at 65'.

    This is correct isnt it ?!

    David
    DAVID_HX_XP_RX-DI

  6. #6
    Joined
    Feb 2001
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    Clearwater, FL
    Posts
    7,358

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    Ack, DUH - I can't read! [img]redface.gif[/img]

    Yes, that is correct. Basically, when you factor in the duration of the valve (159), the timing mark (65), and the height of the port (53) - it all works out the same. Timing to either spec is the same position for the valve.

  7. #7
    Joined
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    KNOXVILLE TENNESSEE
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    Thanx Bryan,,,,,

    This has all been a very interesting (albeit expensive) learning experience for me. Taking it all in stride though (until the VISA bill comes in......... LOL)

    Still need to find someone with some insight for '96 HX OEM Carb. & F/A jetting, Pop-Off N&S, H/S~L/S adjustments when using a Factory Pipe at 813 ft. elev.
    Bill @WCM dosnt use OEM carbs. and didnt offer anything to my inquiry.
    I know what Ross Liberty at the Factory says and I have been in ongoing conversation with him while using the FP Carb. specs that came with the pipe kit. Its just that I dont want another expensive Geothermonuclear Meltdown to my front piston again !!

    ( The plugs were always very dark and slightly oily wet)

    David
    DAVID_HX_XP_RX-DI

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