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Thread: 951 issues

  1. #1
    Duke's Avatar
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    951 issues

    Why is it that one of the most simple 2strokes on the planet is such a pain in the ass!! Seriously!!

    OK, ski has great spark, fuel, turns over fast and even with boost won't fire. Ski ran great the week before and decides to ruin my wifes mothers day by not starting.

    Don't get me wrong, ski is no virgin in any way. She was a SS with Coffman and reflashed MPEM for many years and I just got tired of the upkeep. Backed down to a white pipe with Dean port specs but recently just being a major pain in my ass.

    If it were up to me there would be 2 conversions in the garage but my lovely, (slightly demanding ) wife is in love with this hull.

    Thought the flywheel might have crushed the keyway but no deal. The ski will turn over forever and give the occasional backfire. Tried diff fuel, plugs, major batt boost, starting fluid, plugs, etc..

    Any ideas before the match goes in the hull??

    Thanks!


  2. #2
    BLACK MAGIC HEADERS hydrojunkie's Avatar
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    Quote Originally Posted by Duke View Post
    Why is it that one of the most simple 2strokes on the planet is such a pain in the ass!! Seriously!!

    OK, ski has great spark, fuel, turns over fast and even with boost won't fire. Ski ran great the week before and decides to ruin my wifes mothers day by not starting.

    Don't get me wrong, ski is no virgin in any way. She was a SS with Coffman and reflashed MPEM for many years and I just got tired of the upkeep. Backed down to a white pipe with Dean port specs but recently just being a major pain in my ass.

    If it were up to me there would be 2 conversions in the garage but my lovely, (slightly demanding ) wife is in love with this hull.

    Thought the flywheel might have crushed the keyway but no deal. The ski will turn over forever and give the occasional backfire. Tried diff fuel, plugs, major batt boost, starting fluid, plugs, etc..

    Any ideas before the match goes in the hull??

    Thanks!
    POSSIBLY A CRACKED REED PETAL.

  3. #3
    Moderator RX951's Avatar
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    I agree, a cracked reed petal can cause this. if the motor were apart, I would be asking questions like what mag cup you have, year model, yada, yada, yada.....

    but, since it has been running, I would assume a cracked reed petal. All it takes is one backfire to crack a reed as well.

    you got one coil or two? what year is this 951? 98/99? I wonder can it be the P/U coil

  4. #4
    speedskixp's Avatar
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    If your getting good spark and fuel but wont start and you tried fresh fuel it would seem to me that it would be a timing issue such as broken key way (you checked) or a bad mpem or pick-up. I think ot would still start with a broken petal.

  5. #5
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    Quote Originally Posted by hydrojunkie View Post
    POSSIBLY A CRACKED REED PETAL.
    Quote Originally Posted by RX951 View Post
    I agree, a cracked reed petal can cause this. if the motor were apart, I would be asking questions like what mag cup you have, year model, yada, yada, yada.....

    but, since it has been running, I would assume a cracked reed petal. All it takes is one backfire to crack a reed as well.

    you got one coil or two? I wonder can it be the PU coil

    Ya, thought of that too. Rinaldi reeds look perfect inside and out.

    I've got this thing spread out all over the garage and need it running by next weekend. Really pisses me off that such a simple POS has got me by the balls. Would rather build a S3 conversion by Friday then figure out this POS!!

  6. #6
    Duke's Avatar
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    Quote Originally Posted by speedskixp View Post
    If your getting good spark and fuel but wont start and you tried fresh fuel it would seem to me that it would be a timing issue such as broken key way (you checked) or a bad mpem or pick-up. I think ot would still start with a broken petal.

    Thought for sure it was the keyway, yanked motor out and figure it would be back in tonight running!! Wrong. Has fresh fuel, same as whats in the black boat and same time. Installed the RXX Mpem and key and did the same thing.

    Petals are perfect.

    Can a bad pickup coil cause this?? Is there an Ohms test??

  7. #7
    Engine turns over
    • Faulty component in the fuel injection
    system (RFI and DI models)
    • Check for fault codes with the VCK
    (vehicle communication kit). Refer to
    Diagnostic Procedures in ENGINE
    MANAGEMENT
    • Engine drowned mode is active • Release throttle lever
    • Low battery voltage • Recharge or replace battery
    • Low or no fuel pressure
    (RFI and DI models)
    • Check fuel pump operation
    • Check fuel pump pressure output
    • Check air/fuel rail
    • Check fuel pump fuse
    • Check wiring harness
    • Fuel injectors not working
    (RFI and DI models)
    • Check fuel injector operation. Replace
    as necessary
    • Check output signal from MPEM
    • Low or no air pressure (DI models) • Check air/fuel rail
    • Check air compressor system
    • Check RAVE valve system for leaks
    • Direct injector not working
    (DI models)
    • Check direct injector operation
    • Check output signal from MPEM
    • No spark at the spark plug • Check spark plugs condition and
    replace as necessary
    • Check ignition system and repair
    • Defective MPEM • Replace MPEM
    • Defective crankshaft position sensor • Check operation of CPS and replace if
    necessary
    • Fuel water-contaminated • Check/siphon and refill
    • Dirty fuel filter • Clean/replace
    • Fouled or defective spark plug • Replace
    • Water in engine • Check, refer to section MAINTENANCE
    • Carburetion (carburetor models) • Check, refer to section FUEL SYSTEM
    • Ignition • Check, refer to section ELECTRICAL
    SYSTEM
    • Flooded engine
    – Carburetor needle valve stuck open
    (carburetor models)
    • Check, refer to section FUEL SYSTEM
    • Excessive rotary valve clearance
    (if so equipped)
    • Check, refer to section ENGINE
    • Incorrect rotary valve timing
    (if so equipped)
    • Check, refer to section ENGINE
    • Internal engine damage • Check, refer to section ENGINE
    • Sheared flywheel key • Check timing mark, refer to section
    ELECTRICAL SYSTEM
    • Incorrect rotary valve timing
    (if so equipped)
    • Check, refer to section ENGINE

    A motor only needs three things too start, fuel, air and spark, but they must occur together to run properly. Where you said it ran last week, it could be a reed petal or electrical such as the MPEM. I'd check the reed petal first. Is the motor carb or DI? That will help narrow it down too.

  8. #8
    Duke's Avatar
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    Quote Originally Posted by jwick86 View Post
    Engine turns over
    • Faulty component in the fuel injection
    system (RFI and DI models)
    • Check for fault codes with the VCK
    (vehicle communication kit). Refer to
    Diagnostic Procedures in ENGINE
    MANAGEMENT
    • Engine drowned mode is active • Release throttle lever
    • Low battery voltage • Recharge or replace battery
    • Low or no fuel pressure
    (RFI and DI models)
    • Check fuel pump operation
    • Check fuel pump pressure output
    • Check air/fuel rail
    • Check fuel pump fuse
    • Check wiring harness
    • Fuel injectors not working
    (RFI and DI models)
    • Check fuel injector operation. Replace
    as necessary
    • Check output signal from MPEM
    • Low or no air pressure (DI models) • Check air/fuel rail
    • Check air compressor system
    • Check RAVE valve system for leaks
    • Direct injector not working
    (DI models)
    • Check direct injector operation
    • Check output signal from MPEM
    • No spark at the spark plug • Check spark plugs condition and
    replace as necessary
    • Check ignition system and repair
    • Defective MPEM • Replace MPEM
    • Defective crankshaft position sensor • Check operation of CPS and replace if
    necessary
    • Fuel water-contaminated • Check/siphon and refill
    • Dirty fuel filter • Clean/replace
    • Fouled or defective spark plug • Replace
    • Water in engine • Check, refer to section MAINTENANCE
    • Carburetion (carburetor models) • Check, refer to section FUEL SYSTEM
    • Ignition • Check, refer to section ELECTRICAL
    SYSTEM
    • Flooded engine
    – Carburetor needle valve stuck open
    (carburetor models)
    • Check, refer to section FUEL SYSTEM
    • Excessive rotary valve clearance
    (if so equipped)
    • Check, refer to section ENGINE
    • Incorrect rotary valve timing
    (if so equipped)
    • Check, refer to section ENGINE
    • Internal engine damage • Check, refer to section ENGINE
    • Sheared flywheel key • Check timing mark, refer to section
    ELECTRICAL SYSTEM
    • Incorrect rotary valve timing
    (if so equipped)
    • Check, refer to section ENGINE

    A motor only needs three things too start, fuel, air and spark, but they must occur together to run properly. Where you said it ran last week, it could be a reed petal or electrical such as the MPEM. I'd check the reed petal first. Is the motor carb or DI? That will help narrow it down too.
    Not a DI, 99 is carbed, reeds are perfect.

    Thanks tho.

  9. #9
    Did you change the mag cup at all? If it got moved it will cause the motor to backfire. Is it backfiring out of the carbs or the exhaust? That will make a difference.

    Also, check the carbs, on the inside where the pop off spring is, make sure that the arm and rocker pin is sitting flat, not slanted or up on one side allowing too much fuel to come through the needle and seat. I put one all back together and checked again after having way to much fuel into the motor. Are the plugs wet at all when after you crank it over? I could dump fuel out of my plugs when I had that problem.

  10. #10
    Duke's Avatar
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    Quote Originally Posted by jwick86 View Post
    Did you change the mag cup at all? If it got moved it will cause the motor to backfire. Is it backfiring out of the carbs or the exhaust? That will make a difference.

    Also, check the carbs, on the inside where the pop off spring is, make sure that the arm and rocker pin is sitting flat, not slanted or up on one side allowing too much fuel to come through the needle and seat. I put one all back together and checked again after having way to much fuel into the motor. Are the plugs wet at all when after you crank it over? I could dump fuel out of my plugs when I had that problem.

    Boat went from running perfect one weekend to running like this. Backfires are thru the exhaust.

    Mag cup??

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