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  1. #1

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    Old .46 LSN question

    Here is a picture of an older .46 that I recently purchased. The engine appears to have never been run outside of Dub's initial run at the factory. The TDC pinch is amazing. But I do have a question on the low speed needle. What should I set it to prior to the first run? It's no longer set to what it would have been during the initial factory run.

    Also, do I need the metal gasket that goes between the case and the muffler? I have one with my other SJ .46 but this one did not come with one.

    iAlex
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  2. #2
    bob27s's Avatar
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    RE: Old .46 LSN question

    Hi!

    Thanks for writing and sharing the photo.

    That is indeed a very original SJ-46! The stub-needle on the low speed mixture was only on very early engines.

    Setting the low speed - typically the screw portion should be flush. If this is in too far, the engine will have difficulty at any throttle setting. So best to start a bit further out.

    Allow me to offer the following off of the engine instruction sheet. I believe this will get you were ya need to be !


    SETTING THE IDLE: DON'T CHANGE THE IDLE UNTIL YOU HAVE RUN THE ENGINE-IT IS ALREADY SET. Your idle setting should be fairly close from the factory, so try it as-is first. Look at the nut holding the throttle arm. The idle needle should be about flush (even) with the end of the nut. If not, this is a good place to start. (my experience is that this position is about 1/2 to 3/4 turns rich, but start here anyway)

    Open the throttle and set the high speed to about 500 below peak. (see below) Warm the engine and pull the throttle back. Set the throttle at 1/3 open, i.e. the opening should be about 1/8" (3 mm) wide. Let the engine run and stabilize for 10 seconds. Pinch the fuel line closed. Does the engine speed up and die? If so, it's too richturn the idle in (clockwise) 1/4 turn. Repeat, warming at full throttle, pulling back to 1/3 throttle, allowing the engine to stabilize for 10 sec, pinching the tubing until the engine dies within 1-2 seconds. At this point, the carb should be within 1/4 turn of correct.

    Open the throttle and warm the engine. Pull the throttle back to idle for a few seconds. Push the throttle slowly to full. If the transition is not smooth, or if the engine stalls (except for a slight pause to pipe up) try 1/8 turn leaner. If the idle is too lean, the engine will not transition past the 1/3 open point without sagging or dying. Continue this procedure, moving only 1/8 turn increments of the idle needle until you have a slow, reliable idle and a rapid transition. Remember, warm the engine before working with the idle and transition settings. Occasionally, someone gets the idle so lean that the high speed will not work. Open the idle needle and start over if this happens.
    Importnat take-away here the low speed mixture is not 100% an idle mixture. It is more a low speed mixture. Tiny adjustments mean alot. So you want to make adjustments at a "High idle".

    Also.. be sure to run a "hot" plug. Merlin Hot HD, Hangar 9 performance plugs, K&B1-L, OS #3, Enya #3, McCoy 59 are all good choices. Helps transition and idle quite a bit.

    Let me know how you make out, and feel free to contact me with any other questions.

    Bob
    Bob Brassell
    Jett Engineering - Engine Mfg Support Forum Host
    rjbrassell@gmail.com or bob27s@hotmail.com
    RB-78

  3. #3

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    RE: Old .46 LSN question

    I have a stock of several new K&B 1-L's so I wil be sure to use one. Do I need to worry about the lack of a metal gasket between the engine case and the muffler?

  4. #4
    bob27s's Avatar
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    RE: Old .46 LSN question

    sorry for the delay..

    no, no need to worry. We ran them without the gasket for quite a while.

    But if you can find one, always good to add. Gasket that would fit an old K&B61, ST40 or older Webra 40 will also fit.

    Dub can get you gaskets quickly too.

    Bob
    Bob Brassell
    Jett Engineering - Engine Mfg Support Forum Host
    rjbrassell@gmail.com or bob27s@hotmail.com
    RB-78


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