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  1. #1
    CB750 Member Logolibre's Avatar
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    Nov 2018
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    Belarus
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    Question Oil in exhaust. Engine is unstable

    I own a Honda CB750 F2C Boldor (1983)
    After buying a motorcycle for a while was turned on - did the engine work fine. Rustled only cam chain
    I replaced the cam chain and guides, replaced the gaskets and valve seal, checked the pistons and cylinders (everything was OK, compression 8.3-8.5)

    After, for various reasons, the motorcycle stood more than 2 years. After the break, he wound up without problems, the engine worked smoothly. But after a short work (the motorcycle worked for no more than an hour), the engine began to work unstably, white smoke appeared from the right muffler. Only from the right muffler. And it does not pass after the engine is warming up.
    There is a funny video - https://youtu.be/zZWzjbtW5_Y

    And oil began to appear in it. Lots of oil.
    Unfortunately I do not have a photo, but the oil just drips from the place of attachment of the muffler to the pipe.


    While I just checked the candles (3 and 4 cylinder - black, in oil). And checked the compression - it is normal in all cylinders.
    I havenít taken my head off yet, but maybe someone can tell what could be the problem?

  2. #2
    CB750 Addict Wez_'s Avatar
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    Apr 2017
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    Enfield, CT
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    Sounds like a valve stuck open or close. Burnt or broken valve. If the rings are bad, then oil will get into the cylinder and also show good compression. A leak down test should isolate top end problems. Let the air sit in each cylinder for a few minutes encase they are full of oil and check all cylinders. If the leak down test is OK, then I would suspect your rings are worn or bad. Dirtdigger, is that accurate info?

  3. #3
    CB750 Member Logolibre's Avatar
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    Wez, thanks for the answer.

    The problem was solved by replacing the valve stem seals (there were some cracked ones) and the piston rings had to be replaced - the gaps were out of tolerances.

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