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  1. #1

    Join Date
    Jul 2013
    Location
    Roanoke, VA
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    16

    250x w/mods still low top speed

    Trying to sort out why my 250x seems a bit slower than average - mods are:

    BOV blocked
    Bypass valve hose routed out rear seat vent
    IC "cooler" twin bottom feed with top drain
    Secondary waterbox delete
    6 degree timing advance mod
    **Ski is otherwise stock and untouched**

    Performance:

    65mph (GPS), 7600rpm (digital dash guage at WOT), 10psi (dash LCD at WOT)
    Conditions - air and water temps in mid 80's, 6-12" chop, 3/4 tank fuel

    I've checked for boost leaks, engine oil level good, clear tube empty, IC clean, SC bearings smooth, new SC belt, cleaned SC pulleys, SC lobes look OK using small inspection mirror. Pump brgs smooth, impeller looks good clearance is .006-.008" depending on where I measure.

    Ski seems to run very well, does not misbehave at all. Mods above made a very noticeable difference in throttle response plus low and midrange acceleration.

    Do these numbers seem reasonable?

    Could the dash LCD boost gauge be inaccurate?



    '07 250x
    '06 RXT 215
    '01 RXX (75mph GPS)
    '96 XP (heavily modded)


  2. #2
    benjahw benjahw's Avatar
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    Jan 2008
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    Naples, Fl
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    467
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    Riva plate if your after some top end speed. Maybe 1 or 2 degree wedge as well. 10 psi seems low. Is your belt tightened where it needs to be? AIR MODS. Put some washers in between Hull and rear grab bar so the engine can breathe better. Also remove your hoses that go to your BOV and air intake. Riva filter under glove box too.

  3. #3
    benjahw benjahw's Avatar
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    Listed air mods can possible take water into engine so if riding in rough or submarining dont do them all

  4. #4

    Join Date
    Jul 2013
    Location
    Roanoke, VA
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    16
    Belt is nearly new (>3hrs) and checked w/Kawi tool before each ride - pulleys clean.

    I forgot to mention I have the under glove box filter. BOV is blocked and hose removed, bypass valve hose routed out through under seat vent (easy to check for leak at WOT plus pulls heat out of hull at low speed. Thanks for clarifying the "washer mod" I searched but couldn't find where the washers were supposed to go. Sounds like a good idea, I don't submarine often just in rough stuff. How many washers/ how thick a spacer do most folks use?

    I'm planning to change out the plate, torn between Riva and R&D. Most of my riding is on a lake with lots of traffic in the main channel, not uncommon to have 2-3' wakes in narrow spots but most is 1-2', when it's not busy 1' chop or less is the norm. More top end speed would be nice but don't want to degrade the handling in 2' or so wakes. I can keep it pinned through most local conditions now, and want to keep it that way. What I read about the Riva says it may cause excessive porpoising, but not sure if my conditions are rough enough to cause this... Got a recommendation?
    I also plan to add sponsons (like em on my XP and RXX) and remove the center bar on stock grate.

  5. #5
    devils ride 250's Avatar
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    Mar 2010
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    lehigh valley pa
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    I have simar mods. I have the r/d plate and 1' wedge. Solas 16/21 prop. I hit 69-70 GPS. It's been a while since I checked. Took away from handling in the turns a little bit tho. That was on a smooth day and 1/4 tank.

  6. #6
    stangbang's Avatar
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    Oct 2007
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    I don't think you are going to gps your best speeds in 6 to 12" chop. Plus you need a ride plate and intake grate to get more top speed. A 1 to 2 degree wedge will add some top speed also if you aren't into carving corners. Fresh plugs?

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