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  1. #1

    Stumped-Problem with a 1995 657X Carb Rebuild

    I am having a problem with my high speed adjusters on the motors of my boat after my carb rebuild. It is a 1995 Seadoo Speedster with the dual 657X motors. The carbs are the dual setup(four carbs total). Both motors are showing the same results, both were rebuilt at the same time. I have rebuilt several (3) other carbs before, so Iím not totally ignorant on the carb rebuilding issue.

    After my rebuild the high speed adjusters are at 3 turns out, and they barely are acceptable looking at the plugs after doing a high speed chop. Before the rebuild the high speed adjusters were approx at ľ turn.

    From memory the high speed jet is 132.5 and the low speed is 65. The jets were never changed, and I was able to look through them and the passage ways while shinning a light through from the back side. Pop off was set at approximately 21psi. Needle and seats were reused and are not new.

    I have checked the feed input and output fuel lines(check valves) by doing the following:
    For input- blowing into the intake(gas passes) and vacuum (gas stops)
    For output- blowing into the outtake(gas stops) and vacuum (gas passes)


    I changed the following:

    1-Replaced the Pulse lines w/new fuel injection hose rated at 60psi. I have tried one other type of hose that is a hard plastic rubber type with no better results.
    2-Carbs were totally cleaned with carb cleaner, all parts and gaskets/o-rings, seats, adjusters were removed first.
    3-All new Gaskets/O-rings, pump diaphrams were used except I reused the Needle & Seat. Everything else is new. The needle & seat tip looked good with no wear or indentations so I reused them.
    4-New carb to intake manifold gaskets were used. Mating surfaces were cleaned very well. I even removed the carbs a second time and replaced the gaskets again thinking it was a leaky gasket. No improvement.
    5-Carbs were removed and taken apart a second time looking for problems. None found.

    Any ideas?


  2. #2

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    double check O ring on rotory valve cover,maybe wrong one
    + check crank seal

    later cd

  3. #3

    Rotary valve was never removed

    Rotary intake was never removed, neither was the lower end.

    Being that this problem didn't occur until after the carb rebuild, I was thinking it was something associated with the rebuild itself.

    I did use an aftermarket carb rebuild kit, it was not a mikuni rebuild kit.
    Maybe I should have used the Mikuni kit.

  4. #4

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    did you check fuel pump ?

    later cd

  5. #5

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    sounds like your just washing the plugs with a ton of gas, close the highs back up to the original specs, install a new set of plugs and run it around for 30 minutes or so to color up some, check the plugs, then do some high speed runs.

    TLR

  6. #6
    96XPSS's Avatar
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    Did the carb rebuild kit have new mica check valves for the fuel pump? How did the engines run before the rebuild? Good, bad? Lean, rich? Take us pics of the plug chops...right after nailing the gas wot, just in case you are lean.

    Pulse line is my main concern. I'm an 800 and newer dude, so bear with me. Is the pulse line longer than the original? It has to be something you did to both engines since it's common now to both. Let me know how the engines ran previously...then we can help.

  7. #7

    yes

    Yes, the problem seems to be common to both engines. Both were done at the same time. And yes, I tried a different Pulse line also. No joy ! Both Check valves were replaced too. It was running very rich before, I found tears in the check valves on both motors.

    All components replaced except both jets & needle and seats.
    I turned the HSJ back to 0 and tuned forward. Ping city !
    I instantly started turning the HSJ open in 1/4 increments until ping just disapeared. At this point I was at about 1 1/2 turns out. Plugs color like they should at about 3 turns out. This is way too much.

    I was thinking that since I used a non-Mikuni brand rebuild kit that there was something wrong with the kit. I used a Gasket Technology Mikuni 38/44/46 Super BN Carb Rebuild Kit. ;(


    Any one else have a problem w/ Gasket Technology parts?

    Specifically the carb rebuild kits?
    Last edited by scooter123; 09-26-2007 at 01:27 PM. Reason: typos

  8. #8
    96XPSS's Avatar
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    I'm not familiar with the brand you used, but I think the diaphrams are either different material or the center pin is shorter than the Mikuni diaphrams. Either will prevent the needle and seat from fully opening, as this pin is what pushes on the arm to lever the needle off the seat. If you have two good diaphrams out of the 4 old ones, try installing them on one engine and see if this clears it up. Also a close visual of the Mikuni versus the others might show a difference.

    Did you check the Mica check valves in the fuel pumps too?
    Last edited by 96XPSS; 09-26-2007 at 04:47 PM.

  9. #9

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    one other ? how old fuel

    later cd

  10. #10

    I'm thinking that

    Gas is good. Check valves in pump verify ok.

    I've been thru 2 tanks now of gas from different places. I'm currently running at about 3 turns out on all carbs which produces somewhat good or barely acceptable results.

    I'm thinking possibly that: A) The pump diaphrams(the thin plastic sheet on the pump side that pumps fuel) is not as flexable as the mukuni. Or B) That the needle/seat diaphram actuator material is not as flexable or is thicker. Or C) That the diaphram that actuates the needle/seat is not pushing the needle open enough (possibly the tab in the center is not long enough?).

    I'll have to compare them to the old.
    My take on it is that the carbs are not getting enough fuel somehow.

    If its B & C above, Can I adjust(bend) the needle/seat lever arm up slightly? Maybe .020" to .030" ? This would allow less diaphram movement to open the needle.



    The funny thing is that with 2 motors(both show the same problems) and dual carbs each motor (4 carbs total) I am getting the same results.

    Go figure.

    Any other ideas?

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