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BSA A10 additional breather

Discussion in 'BSA' started by baz, Mar 22, 2020.

  1. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    I'm considering fitting a reed valve breather to sump plate on my A10
    Like the type cnw sell for the commando
    This would solve my wet sumping issues and maybe help with oil leaks
    What's the opinion on this?
     
  2. Matchless

    Matchless

    Joined:
    Dec 23, 2010
    As long as the inlet tube to the reed valve was above the oil pickup level it should be okay. If not it would interupt the return oil feed. A pit bike reed works if you can machine a housing to suit. Reed valves work really well & it seems that most modern twins are fitted with one. On my 920 it cured a slight oil misting from the base gasket face when cruising at 90+ & it is completely oil tight.

    Martyn.
     
  3. Triton Thrasher

    Triton Thrasher

    Joined:
    Feb 10, 2009
    Don’t put a breather on the bottom of the engine. It will pump oil out.

    You want it at a height near the top of the timing cover. Even then it might be oily.
     
  4. Matchless

    Matchless

    Joined:
    Dec 23, 2010
    The reed on my Commando is at the base of the crankcase in the Combat type breather position. This is higher than the pickup level but low enough to pump any oil back to the tank due to wet sumping after standing for months. The important thing here is you MUST run the reed to the oil tank & then vent the oil tank as well.
     
  5. Triton Thrasher

    Triton Thrasher

    Joined:
    Feb 10, 2009
    So he has to plumb the oil tank in and out and fit a standpipe upwards from the sump plate, high enough to let the scavenge pipe work normally and feed the rockers, but the standpipe must be a safe distance from the flywheel and big ends.

    It really sounds like a pointlessly difficult way to fit a breather.
     
  6. Matchless

    Matchless

    Joined:
    Dec 23, 2010
    Jim Comstock worked out the most effective position for the reed valve was in the crankcase, preferably with the timing chest vent holes blocked off. He makes two versions, one of which screws into the sump plug & seems to work very well on Norton twins, but as I'm not all that familiar with A10 motors it would be trial & error. No harm in trying though if you can be bothered. Even if it was fitted at the top of the timing cover it would still need to be vented to the oil tank.
     
  7. Triton Thrasher

    Triton Thrasher

    Joined:
    Feb 10, 2009
    A breather high in the timing case may not have to be directed into the oil tank. The one on my Triumph isn’t.
     
  8. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Sorry I hadn't realised anyone had replied until it was pointed out to me on the A7 A10 forum
    I have fitted a pipe to the sump plate with an inline reed valve at above engine height
    Everything works fine there is no oil coming out and virtually no pressure
    Oil is returning the same etc
    I tried removing the reed valve the bike runs the same
    There's a bit of gurgling in the pipe but that's about it
    Virtually no pressure or suction
    I have extended the breather tower on my oil tank so I have an extra breather pipe above the existing one
    I plan to connect my sump plate pipe to the reed valve at carburettor height then to the lower breather on the oil tank
    The upper breather from the tank with vent to the back of the bike
    I still have the standard rotary timed engine breather fitted this appears to be working very well as there is virtually no pressure or vacuum from my additional pipe on the sump plate at low revs or high revs
    The oil is returning fine as said, what have I missed?
    The bike is used infrequently and I wanted to try this mainly to see if the effect on the wet sumping
    Cheers
     
  9. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    The bike is now up and running and appears to be working perfectly
    The pipe comes from the sump plate to the reed valve fitted behind the geabox then to the oil tank tower
    I have fitted an additional tower on top of the original one
    This is tee'd to the original breather then vented to the back of the bike
    All seams well there is no oil coming out of the reed valve
    There is very little pressure coming out of the reed valve, testament to BSAs timed breather I'd guess?
    Gave the bike a good run today it's fine at 80mph so I'm hoping it's a worthwhile conversion only a few hours work
    I'm hoping when it wet sumps the oil will be returned straight to the oil tank
    Very pleased so far cheers IMG_20200402_191759068.jpg
     

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