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  1. #1

    Join Date
    Feb 2011
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    Location
    Georgia
    Mower
    Craftsman

    16.5 B&S v-twin valve adjusment

    A few weeks ago I found this forum when searching on info for adjusting the valves on my Craftsman 18.5 HP mower. I got the info I needed, went home and now she fires up perfectly.
    I told my father I would help him adjust the valves on his mower because he was having the same problem as mine. Engine will only make one or two rotations, but won't turn enough to crank. It's not the battery or starter. However, I later found out his motor is a 16.5 HP v-twin (B&S 42A707-2238-E1) which is nothing like mine. I'm looking for instructions on how to adjust the valves. Any help or advice will be appreciated.

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  3. #2

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    May 2010
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    Illinois
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    kioti/rhino finish mower

    Re: 16.5 B&S v-twin valve adjusment

    That is not a v-twin. that is what the dealers refer to as a opposed twin. To adjust the valves you remove the heads, remove the intake manifold, remove breather covers, remove valves and adjust clearances by grinding the stem a little at a time to get the proper clearances. I dont think the valves are the problem here. I have seen starters turn like they are good on those engines and still be bad. cranks slowly, wont overcome compression stroke, may start sometimes and not others are symptoms I have seen.
    ILLINOIS ENGINE, BEECHER CITY, IL
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  4. #3

    Join Date
    Feb 2011
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    2
    Location
    Georgia
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    Craftsman

    Re: 16.5 B&S v-twin valve adjusment

    Thanks. I certainly don't want to get into valve adjustment if that's not the problem. I'll try to rule out starter before getting into anything else.

  5. #4

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    Aug 2010
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    1,250
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    Florida
    Mower
    Ford

    Re: 16.5 B&S v-twin valve adjusment

    Quote Originally Posted by WWeitman View Post
    Thanks. I certainly don't want to get into valve adjustment if that's not the problem. I'll try to rule out starter before getting into anything else.
    Take the starter apart and inspect, lubricate the bushings and re-install before you pronouce it dead. Sometimes thats all it takes. Not that disassembling and reassembling a DC motor is all that easy.
    Remember the brushes are spring loaded....
    Last edited by RobertBrown; 03-02-2011 at 09:33 PM.

  6. #5

    Join Date
    May 2010
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    5,438
    Location
    Kansas, Butler county, Just east of DooDah
    Mower
    CTL

    Re: 16.5 B&S v-twin valve adjusment

    I have also found cracked permanent magnets on mower starters... they still work but they draw more current and do not have the torque they should have... so when you have it apart look close for a crack in one of the magnets... KennyV

  7. #6

    Join Date
    Apr 2011
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    8
    Location
    Texas
    Mower
    Murray

    Re: 16.5 B&S v-twin valve adjusment

    Adjusting the valve clearance should not require removing the heads. If want to refurbish the valves then yes. You tube has several videos on adjusting valve clearance. The typical procedure is to remove the valve cover, position the piston on top dead center, use a feeler gauge to check the valve clearance between the rocker arm and the valve. If the space is to far apart then you must loosen the rocker arm nut and adjust with the feeler gauge to the appropriate clearance (usually .004 but check the specs on the engine). In most cases its the exhaust clearance thats the problem. Youtube has some nice videos on this.

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