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rotary valve timing

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  • rotary valve timing

    I have a 580 seadoo sp. About 1 year ago the engine was rebuilt and it ran great making 6700 rpms (it has a few mods, 44 carb, FPP pipe, ss prop.). Recently the oil injectin failed and it smoked the pistons. I had it rebuilt again with new sleeves and pistons, and now it only makes 6600 rpm. It also appears much quieter and smoother when riding at WOT. I am not really complaining because it runs great, it even appears to have more bottom end torque, but I am curious to where the 100 rpm went? The original engine builder told me he just installed the rotary valve (timing) from experience, he couldn't give a degree value. Now it is installed at precisely what the book recomends. It is a OEM replacement 147 degree valve. Is it possible that the original engine build had a higher revving timing setting? what effect does valve timing have on performance if I were to advance it a tooth, versus retarding it a tooth? Can I actually do this? Thanks for the input.
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