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  1. #1
    Join Date
    Sep 2021
    Location
    Adelaide
    Age
    73
    Posts
    117

    Default Reed valve engine breather.

    I made this little gizmo yesterday, finished it off this morning with the bead blaster. I was going to polish it, but damn this gizmo looks good with a bead blasted finish.
    Petal was taken from a pit bike read valve and cut in half, two holes drilled and screwed to the base plate. Base plate was tapped M3 10mm deep to take the petal. Not fun tapping this small, but, this time around the tap survived.
    Main body was carved out with an endmill to give the petal room to move and air to flow. Base plate has a channel on the engine side for any oil to run down back into the rockers. Topside was channelled either side to get the Allen heads level with the top surface. Stainless Allen's were turned to make them shiny, I do like shiny baubles.
    Outlet spigot is 16mm with a 10mm hole. If it's not big enough I can take it out to 12mm later on.
    Air from the engine enters the main body from the reed valve is channelled upward, does a U turn and travels downward to the outlet spigot, losing a little oil on the way. Any oil trapped before the reed valve is channelled back to the rockers.
    I'll have to design and build a catch can now, thinking of mounting it behind the downtube between the carbs. But, it's getting a little busy in that area.
    Manual machining only, would love a CNC, but not in my budget, would've made things a lot easier
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  2. #2
    Join Date
    Oct 2004
    Location
    Southern Highlands NSW
    Posts
    1,908

    Default

    Very nice. It looks far more engineered than the breather valves that were fitted to Ducatis of the same era as your Yamaha.
    Even the hugely expensive sporty models had a crude looking welded steel housing with a piece of rubber as a flap valve.
    I guess that's all that is needed for a breather.
    Attached Images Attached Images

  3. #3
    Join Date
    Sep 2021
    Location
    Adelaide
    Age
    73
    Posts
    117

    Default

    I did contemplate rubber for a better seal, but didn't think it would last that well. We'll see! As long as it can maintain a negative crankcase pressure that's all the matters.

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