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  1. #1
    CB750 Addict dan1951's Avatar
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    1971 sohc breather hose

    Hi everyone long time since I was on here, Anyway I have a lot of air coming from the tappet cover when running at idle I thought this pressure was released out the breather hose nothing comes from it if it is it is unnoticeable any help much appreciated. Thanks

  2. #2
    CB750 Addict dan1951's Avatar
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    My mistake I removed the breather hose and have it hanging on the side of the bike there is a minimum amount of engine air discharging from it but it is nothing like removing a tappet cover.

  3. #3
    CB750 Guru amc49's Avatar
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    Confusion between true blowby and simple air displacement from pistons going up and down. A four cylinder moves air around a lot as one piston goes down and the one next to it goes up, the air swaps sides and in pairs. That is different from the true blowby which leaks past the rings and normally a much smaller amount.

    On true race bikes you can open up holes in the crankcases to let that left and right alternating air mass change places much easier, it's said to be worth up to 5 hp at extreme rpm.

  4. #4
    CB750 Addict dan1951's Avatar
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    Thanks amc for the explaination.

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