650sx running lean on back cylinder HELP!
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  1. #1
    PWCToday Newbie bassace2003's Avatar
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    650sx running lean on back cylinder HELP!

    Hello everyone. I have a problem with my 91 650sx. The rear cylinder is running lean. Here's some info on the ski. 91 650sx with 180 compression on both cylinders. 42 cdk2 keihin race carb, west coast pipe, west coast exhaust manifold, dg intake, carb jets are 155 and 82. Fresh rebuild on carb, good spark on both spark plugs. I can get it started and running but the motor surges really bad beyond half throttle. The back spark plug is white and front plug is brownish tan like it should be. Really could use some help with this as it's got me stumped. Thank you!!

  2. #2
    Top Dog FOG's Avatar
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    Re: 650sx running lean on back cylinder HELP!

    Check the intake tract gaskets and the reeds. Compression test will not indicate whether or not reeds are good. Might also have failing rear crank seal.
    I'll quit before I sit~~~

  3. #3
    PWCToday.com Is My Home Away From Home hyosung's Avatar
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    Re: 650sx running lean on back cylinder HELP!

    i will go with a leaking crank seal , do a leak down test ,,,
    http://www.pwctoday.com/showthread.php?t=425767

    modded X2 650

    900 powered custom 650 sx .

    Jerry Rigging is my specialty .....



    if i did like everyone else and copied everything i needed or wanted i would save lots of time and money.

  4. #4
    PWCToday Newbie bassace2003's Avatar
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    Re: 650sx running lean on back cylinder HELP!

    Reeds look good to me. image.jpg

  5. #5
    PWCToday Newbie bassace2003's Avatar
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    Re: 650sx running lean on back cylinder HELP!


  6. #6
    PWCToday Newbie bassace2003's Avatar
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    Re: 650sx running lean on back cylinder HELP!

    Going to get a leak down tester today and try to perform the test. I'm really hoping it's not a bad crank seal. Are there any other possibilities?

  7. #7
    PWCToday.com Is My Home Away From Home hyosung's Avatar
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    Re: 650sx running lean on back cylinder HELP!

    cylinder base gasket ! , case sealant melted , hole in crankcase ...
    Last edited by hyosung; 07-23-2015 at 01:50 PM.
    http://www.pwctoday.com/showthread.php?t=425767

    modded X2 650

    900 powered custom 650 sx .

    Jerry Rigging is my specialty .....



    if i did like everyone else and copied everything i needed or wanted i would save lots of time and money.

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