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  1. #1

    1991 650 cc waverunner backfiring

    WHAT DO I DI 1ST THANK U ANY ONE


  2. #2
    I converted from the oil freeder and whent to pre mixed didnt help 50/1
    when on the water it has a small miss in it for i minit or 2 then it gos away
    evan after it warms up.but after i got home just to make sure it started up
    easy then hit the trotle wide open then it back fires through eguse .
    I did the carb ajust best i could with it tied up in the water.for the low end stated at
    2 out on the low end and 3/4 out on top end the went in 1/8 un till i got it to take off
    and go it dose ok . I did put new plugs in ,helped some
    is this problem my coil?
    My cdi?
    My stator?
    It rns kind of fast... Just well.....jjust want to know what the heck is it?
    I did clean the crab ,then i changed the crab from and old 700 cc i had still the same
    thank u for reading any help out there?

  3. #3
    Old Ski Insanity w/rpm500's Avatar
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    Aug 2005
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    Crystal River Fl
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    first of all a 650 and 700 will be jeted different, switch those carbs back..
    for a stock motor 650, your carb needs to be adjusted within these specs...

    low needle is adjusted 7/8 to 1-3/8
    high needle is adjusted 7/8 to 1-3/8

    if it runs better past those specs,youll need to do an internal inspection of the carb and or a jet change if its a modifyed motor to get the needles back within those specs to run best..(mikuni builds a good carb and their sudjested settings are for best balanced fuel flow)

    Id also check:
    for bad fuel, old or water in it...

    my hoses for cracks (sucking air)inside the tank and out..
    your spark plug ends for corrosion...
    clogged filters or screens ( 1 in tank,1 in line and 1 in carb)

    oh and dont peg your throttle when not underload , you can get a run away motor...you may also backfire when you do this as fuel is not burnning off before another charge comes in...

  4. #4
    all rithty thaaannkk u ill change the crabs back i did change the fule,and both filters in and outgoing.
    i cant find any water leaks in the motor ,,looked very hard tooo..
    im on it now ill post results good er bad...i know where to buy
    the kit for the ive not done that yet and dont know how to do the pop off psring in crab.
    what ever 25-30 psi er somthing maybe ya can tell me where to get the tool
    i need for that and how to do it.

  5. #5
    Old Ski Insanity w/rpm500's Avatar
    Join Date
    Aug 2005
    Location
    Crystal River Fl
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    2,208
    if the motors not modded you'll not have to deal with popoff unless the spring is weak..in that case just replace it with the same color..(gray, silver ,gold or black)..
    water,if an issue , is in the fuel, as in condensation..If you had any it may also be in the carb too now..

  6. #6
    ok put the other crab back on did the rebuilt kit and it has a small miss cant seem to get it out
    ive tried every adjustment even in 1/16 turns on da crab i replaced all the fule with new high test
    its still there verrrmmm dhaaaamisss veerrrummmm daaaaaa then miss again its not real bad
    its just there . i put new in plugs again helped a little.
    read valves?
    leak in intake?
    head gasket?
    its goes away for a while at top end then let off gas hit it again and there it is back.
    its like a little gremlin running around under neath the seat.eerrrerrerrererrr...
    thank u

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