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Please help,cast iron,single cyl motor

Discussion in 'Off Topic Threads' started by patrick Swartz, Aug 17, 2013.

  1. patrick Swartz

    patrick Swartz Member

    Joined:
    Dec 30, 2007
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    Gentlemen,

    I have been impressed by the depth of knowoledge that some here, have on a particular subject. I hope to be able to draw on that resource. A friend inherited a 70's or 80's Allis lawn tractor from his father's estate. He has asked me to rebuild the big,old cast single cylinder motor. The rebuild is not the problem for me. What I need to know,is if anyone here has ever successfully re-engineered an inline carburetor for this application to be able to get away from the troublesome,up draft carburetor that came on these old style motors. I think the only reason that an updraft was ever used was to reduce the envelope size of the motor package. Making a new manifold is not a problem. I considered using a motorcycle carburetor with the same diameter venturi area. I can silver solder and redrill the main jet if it wants to run too fat or just open it up if it wants to run lean. The problem is with the amount of travel in the lift style slide valve on a motorcycle carburetor. I don't think that it would be a good idea to put a twist grip on a lawn tractor. If any of you guys have done this,please let me know what you found, that worked the best.

    Respectfully,

    Patrick Swartz
     
  2. GR Eubanks

    GR Eubanks Active Member

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    What a great project. Sounds like you will have fun. Sorry I can't help.

    TTT and good luck
     
  3. 682Fan

    682Fan TS Member

    Joined:
    Jan 29, 1998
    Messages:
    93
    Sounds like you are considering a CV (constant volume) carbureter.
    DO NOT bore out the jets. Low speed jet will function into upper RPM ranges, high speed jet (non adjustable) takes over from there. You can obtain larger jets if truly required, but I seriously doubt you will need to re-jet.
    A choke cable assembly will do for the throttle-obtained at Pep Boys.
    Good Luck
    Arnie

    PS On a used carb, dismantle and clean thoroughly with brake clean or similar agent.
     
  4. Straight99

    Straight99 Member

    Joined:
    Apr 23, 2007
    Messages:
    336
    I have done the same with an older snowmobile carb. I welded an adapter to bolt the carb. on. I have also found side draft carbs from Briggs and Kolar engines that work even better.

    Good Luck
    Glenn
     
  5. Mapper

    Mapper Member

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    SW Michigan
    Hooking up a slide valve carb should be a snap. One can experiment with the length of the lever controlling the carb and make it work. Jets for most Japanese carbs are available at motorcycle shops cheap. The only problem I have had is when the largest piston available would not clean the bore. It ran OK, but used oil. As some one mentioned, butterfly valve carbs are also around and pretty cheap used.
     
  6. halfmile

    halfmile Well-Known Member

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    Green Bay Wisconsin
    If you don't mind it sticking out, I would use a Tillotson. (you can engineer an elbow of some sort to improve that.)Quite a few snowmobiles had them. You can then use a more normal linkage than a slide type.

    I had one on a motorcycle with the diaphragm removed, and it ran like stink. Also had the ability to adjust without changing jets. Had to remember to close the gas petcock all the time, though.

    HM
     
  7. HSLDS

    HSLDS Well-Known Member

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    I'd look at the B & S or Techumseh 'all in one' carbs (the float bowl sits beneath the carb - see image. These should fit just about any sized space you have available). Be sure to match the carb to the horsepower of the engine (at least get close - you shouldn't need to change jets then).

    Your biggest challenge will be to build a 'manifold' to connect the carb to the engine - that being said a lot of old B & S engines had some really convoluted manifolds - one of those might get you really close. Linkage should be the same as what's already there - might need to reposition it a bit.
    hslds_2008_03038.jpg




    -

    Check out above website too - he has lots of odd parts, etc.
     
  8. HSLDS

    HSLDS Well-Known Member

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    Here is another site that might help you - looks like the HP on these went from a low of 6 to a high of 19 - quite a range. I suspect you need to do some research on this before you get started...
     
  9. stokinpls

    stokinpls Well-Known Member

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    Does it have a governor on it? If so, what sort of linkage matchup will you have with the carb in a different place? Maybe they didn't have governors back then. If you do use a float carb, make sure you install an inline fuel shutoff, if it doesn't already have one. Good luck.

    Bob Falfa
     
  10. vodkanockers

    vodkanockers TS Member

    Joined:
    Jul 14, 2013
    Messages:
    29
    Ask these guys here on "My Tractor Forum" This link should take you to the allis/simplicity part of it.

    http://www.mytractorforum.com/forumdisplay.php?f=16


    I rebuild a lot of Garden Tractors for a hobby. If you are dealing with a Briggs updraft, it is a fine working carb if rebuilt right an no vacuum leaks.

    Heres some of mine I have done. 79 wheelhorse C-101 - 80 wheelhorse lawn mower - 72 John Deere 112


    vodkanockers_2013_14072.jpg



    Ron
     
  11. HSLDS

    HSLDS Well-Known Member

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    vodkanockers,

    I grew up on a JD 112 - around 1962 vintage.

    Kohler engine and rock solid - still running today. It taught me an awful lot about small engine repair. Now have a JD 212.

    Got to love something 50 years old that still runs like a top.
     
  12. Bvr Tail

    Bvr Tail Well-Known Member

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    I have had two Simplicity mowers in the past, with the cast iron Briggs in 16 hp.

    If the carb. is in good working order, and the throttle shaft is tight in the bore, these carbs perform good.

    These carbs. don't like any water in the system at all, so clean out the complete fuel system.

    Try the original first, but you might have some fun experimenting with different carbs.
     
  13. chuckie68

    chuckie68 Active Member

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    Why not fuel inject it? Seriously, the envelope for the FI intake is or would be pretty small. All you would need is a short tube to mount the nozzle on and another inch maybe to mount a slide valve air restricter. All the rest of the system could be mounted away from the engine.

    Chuck