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  1. #1
    Join Date
    Aug 2007
    Location
    South West
    Posts
    68

    Engine dies on braking

    From my thread search this seem a not uncommon problem. Down here in the Dung country's lanes I frequently have to brake hard and dive close into the hedge to avoid large 4x4s who seem unable to get anywhere near the hedge on their side. The engine usually dies on anything more than gentle braking. My carb is a BG 650 double pumper speed demon and I am led to believe that a surge goes up the vent pipes on either/both the primaries and secondaries and temporarily drowns the engine. Is this correct? Would adjusting the float levels change this? I saw a post which said that connecting the primary and secondary vents with a small pipe pipe vented at the top of its arc would help. Its getting so that I can't rock up to any junction enthusiastically without an embarrassing stalling moment. Any advice would be gratefully received.
    Thanks

    Tim

  2. #2
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    896
    I had the same problem and addressed it here:

    http://www.cobraclub.com/forum/showthread.php?t=60685
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  3. #3
    Join Date
    Nov 2016
    Location
    Stevenage
    Age
    48
    Posts
    304
    Brilliant just what I’ve been looking for after carb rebuild (600 cfm vs) I have no vent and side hungs as described by you, i can see that the white ones would interfere with the bowls but the shortie may just clear, question did you still drill/tap a screw to hold them in place ? And did you fit them to primary and secondary side ie to deal with the harsh braking and accel?
    I have no baffled presently but have got the engine to idle well and nice low emmission, following a different issue with idle transfer slot over exposure.
    Another question did you base your power valve on vacuum guage reading at idle and divide in half?

    Thankyou.

  4. #4
    Join Date
    Aug 2007
    Location
    South West
    Posts
    68
    Thanks John for your link. ,
    Luckily I have enough room in the air cleaner to connect up the two vents in silicon tube with some air vents more or less as per you first diagram. Must go out and brake violently to see if it works.

    Tim

  5. #5
    Join Date
    Feb 2002
    Location
    Bradninch, Devon, U.K.
    Age
    71
    Posts
    2,343

    Cool

    Tim
    Have you considered it may be your driving style ?
    (Snigger )
    Catch up sometime
    CHRIS C - Maisie (DB No 46 )

  6. #6
    Join Date
    Aug 2007
    Location
    South West
    Posts
    68
    Thanks for that Chris. My driving style is frequently critiqued, usually by my wife, and usually not in a positive way.
    Anyway, as an update after fitting a vented tube to the float chamber vents ........ went out today and tried some heavy braking, coff. The cutting out is far less and engine just about keeps going but its still not as I would like .
    So, with secondaries now (presumably) not drowning the engine, is the stumbling due to fuel level dropping in the primary bowl as it sloshes forward and starving the feed. Any ideas gratefully received.

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