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  1. #1

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    900 STX Oil pump seal leaking

    I am thinking of putting my oil injection system back on my 1999 900 STX. The oil pump however is leaking around the input shaft. I looked on the parts diagram and it does not show a seal for the pump, only the whole pump. Am I missing something or is the pump non serviceable? I think it was working it just filled the Magneto housing with oil. Maybe the oil pump connecting shaft that goes between the oil pump and the crank is supposed to contain the oil. As usual any help or advise would be appreciated. Thanks!


  2. #2
    steve45's Avatar
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    Have you looked at the front seal on the crankcase? When you pulled the oil pump off, was there oil in the cavity where the driveshaft coupling & bearings is?

  3. #3

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    Yes there was oil in there and probably about a half a quart of oil poured out of the magneto housing when I pulled the cover off. I know I need a new bearing for the coupler, it is really rough. Also there is a seal on the input shaft of the oil pump its self that I will need to replace and that should take care of the leaky oil pump. There is no concern needed for the crank seal as this is a different engine.

  4. #4
    steve45's Avatar
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    The oil pump is made by Mikuni. I don't know if there are any service parts available for it. You might find a used one on Ebay if you can't find a seal.

    A blown front seal can leak oil from the front cylinder crankcase. Here's one I had:

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  5. #5

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    Sadly it appears as though the shaft seal on the oil pump is glued in place so getting it out is defiantly going to destroy it. I would think about a used pump but I bet most if not all used pumps are going to suffer the same affliction. Also the coupling shaft and associated bearing that goes between the crank and the oil pump needs to be replaced. Kawasaki refers to this part (44070-3701) as a "Damper" and if you look closely at the picture it seems to have a rubber sleeve around it. So if you just went looking for the bearing you would get the rubberized version. The sleeve must be to reduce the amount of vibration transmitted from the crank to the Magneto housing. So if I really want to go back to oil injection I am going to need to spend about $400 for parts. So not sure if I want to do that or not.
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  6. #6
    steve45's Avatar
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    I've actually never heard of a Mikuni oil pump leaking any significant amount of oil. Wouldn't both me to buy a used one, as long as it's the correct one.

    This article discusses replacing the bearings on the drive coupling: http://www.greenhulk.net/forums/showthread.php?t=258295

  7. #7

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    This is great information, I can save enough money that I should be able to go back to oil injection.

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