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Thread: Linkert MR3

  1. #1

    Linkert MR3


    I was wondering if you can run an MR carb without a fixed jet?

    The holes where the jets go have been drilled out so I made a few plugs and put them in.

    The bike starts but when you open the throttle quickly and hold it there the bike dies. It’s obviously not getting enough fuel. If I hold my hand over the 1/2 the mouth of the carb it happily revs.

    I have the HS needle almost all the way out and no improvement.

    I had a similar problem with the M53 on my race bike and I solved it by putting in a fixed jet.

    1938 WLDR
    1940 WL (Race Bike)
    1944 WL

  2. #2
    Join Date
    Sep 2009
    Missouri City, Texas

    Re: Linkert MR3

    Find someone who could weld up the hole, drill and tap the correct size...

  3. #3

    Re: Linkert MR3

    The original threaded hole in the casting (for both main jet and body plug) is 8-32 NC.
    An old rule of thumb for Linkert Model M main jet size for the 4-bolt carburetors was the square root of engine displacement in inches ÷ 11,000: (D ÷ 11,000)^.5.
    Some results:
    Size, calculated jet ID (OEM carburetor, factory jet)
    45, .064" (M-53 .0649")**
    54, .070" (M-53A1 .070")
    61, .0745" (M-61 .0795")*
    74, .082" (M-74B .082")

    * I suspect the relatively large manifold plenum, large ports & valves, and very high rod ratio (2.13:1) indicate a 14% larger jet to compensate for weak vacuum draw.
    ** the above rule is not followed here because of the strong draw of the booster venturi, a 45 with an M-53A (1-5/16" straight venturi) would use a .068" jet.
    Last edited by panic; 10-05-2019 at 09:31 AM.

  4. #4

    Re: Linkert MR3

    Thanks guys, I appreciate the input.

    I think you’re right Mark. I was hoping someone would say I run mine without jets and it works fine
    1938 WLDR
    1940 WL (Race Bike)
    1944 WL

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