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Thread: Oil reservoir pressure?

  1. #1
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    Oil reservoir pressure?

    It's been about 2 years since ive started my xb9sx. Got a new battery, and she fired right up. After idleing for 5-10 minutes or so i gave a few moderate revs then shut her down because i wanted to check the oil itself, and oil level. As i'm unscrewing the filler cap a bunch of air starts blowing out like it had built up a good amount of pressure. Now i could be mistaken, but i dont ever remember these swingarms/oil tanks building pressure like that.. please tell me i'm wrong, and that this is normal.

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    Senior Member 34nineteen's Avatar
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    Quote Originally Posted by XB9BANE View Post
    It's been about 2 years since ive started my xb9sx. Got a new battery, and she fired right up. After idleing for 5-10 minutes or so i gave a few moderate revs then shut her down because i wanted to check the oil itself, and oil level. As i'm unscrewing the filler cap a bunch of air starts blowing out like it had built up a good amount of pressure. Now i could be mistaken, but i dont ever remember these swingarms/oil tanks building pressure like that.. please tell me i'm wrong, and that this is normal.

    Any motor is going to build up crankcase pressure and it needs to go somewhere.

    You may want to double check to make sure all of the vent lines are clear and flowing. If you allow the bike to build pressure, you like likely blow a gasket and then you will have a gasket leak,. which will be much more problematic and expensive to resolve. Over time insects or whatever may have built nests in the hoses and clogged them. Or the PCV valve(s) are stuck closed from sitting.

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    Thanks 94nineteen. My crankcase vent is free and clear of any blockage, it seems to be only building pressure in the swingarm itself. So theres 3 lines on the swinger, oil feed, oil return, and another line that looks like it goes to the case. Where would i find the pcv valve? Also, is there a slight possibility that the oil being old/dirty and thick that it might have built this pressure? I really didnt let the bike warm up much at all..
    Maybe change the oil and let it warm up to tempereture before unscrewing oil plug?

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    Senior Member 34nineteen's Avatar
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    Quote Originally Posted by XB9BANE View Post
    So theres 3 lines on the swinger, oil feed, oil return, and another line that looks like it goes to the case.
    You mean the vent hose?

    Quote Originally Posted by XB9BANE View Post
    Where would i find the pcv valve?
    The PCV valves are on the top of the valve covers. There are hoses that should go to your air cleaner or wherever they may have been routed afterwards.

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    Senior Member Cooter's Avatar
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    34:19 is giving you good advise (as usual)
    Heres another idea.
    There is a valve between the crankcase and oil tank that stops oil from returning to the crankcase while the engine is off.
    It is probable that sitting so long allowed all the oil in the oil tank to return to the crankcase, emptying the oil tank.
    It's possible that once you started the bike, all that oil is getting pumped (slowly) back into the oil tank replacing the air with liquid, causing the pressure you felt.
    If you have even a little oil in the tank (use a light, don't add some) I would start the engine for ONE minute, listen for bad noises, shut off and re-check the oil. Is there more oil? If so, I'm right, start it again and let it warm up 4-5 min or until the fan starts. Then re-check the oil level.
    The oil needs to be warm, and in the tank to drain it affectively anyway.

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    Senior Member 34nineteen's Avatar
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    Quote Originally Posted by Cooter View Post
    34:19 is giving you good advise (as usual)
    Heres another idea.
    There is a valve between the crankcase and oil tank that stops oil from returning to the crankcase while the engine is off.
    It is probable that sitting so long allowed all the oil in the oil tank to return to the crankcase, emptying the oil tank.
    It's possible that once you started the bike, all that oil is getting pumped (slowly) back into the oil tank replacing the air with liquid, causing the pressure you felt.
    If you have even a little oil in the tank (use a light, don't add some) I would start the engine for ONE minute, listen for bad noises, shut off and re-check the oil. Is there more oil? If so, I'm right, start it again and let it warm up 4-5 min or until the fan starts. Then re-check the oil level.
    The oil needs to be warm, and in the tank to drain it affectively anyway.
    Wet sump Cooter saves the day.

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    Thanks fellas, i'll do that tonight and report back👍👍

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    Update: let the bike idle for a while, everything sounded fine. Shut the bike down, unscrewed filler cap and... no more compressed air! Drained some really ugly looking oil out, swapped filter, new full synthetic, and we're back in business!
    I figured it was probably fine, but thought id be safe and ask. Thanks again for the help🖐

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    Senior Member 34nineteen's Avatar
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    Cooter was probably right dammit!

    Thanks for the update!

  10. #10
    Senior Member Cooter's Avatar
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    Glad it worked out for you and thanks for posting what happened Ride it a bunch! and never start it unless you're going ride it.


    Aaron, I'm sure my guess was total luck



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