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Hot!Briggs engine

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Clipper
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2019/06/13 09:45:11 (permalink)
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Briggs engine

Oops,
I tightened the bolt that holds the flywheel on with a impact wrench and now it’s out of time. The key is all right, but fires a 1/4 turn too soon. Someone told me the magnets on the inside the flywheel are screwed up, but they look o.k. To me. I don’t think the flywheel turned when I tightened it. I know it was a stupid thing to do, but anyone have an idea what I screwed up? It is a 19 hp B&S model 33R877 engine. Any good news out there? Thank you.

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    Roy
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    Re: Briggs engine 2019/06/13 11:36:19 (permalink)
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    How do you know the engine is out of time if the key is not sheared? You may have split the flywheel hub.
    AVB
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    Re: Briggs engine 2019/06/13 13:24:33 (permalink)
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    About the way the engine can fire a 1/4 turn off is for the flywheel to be a 1/4 turn off. Even if you had the coil upside down and most won't even fire they are it would fire delayed [after] instead of before.
     
    It sound more like the flywheel would have be off by 90 degree before; hence, either it is now cracked and unusable or the key was never in place if not sheared.
     
    NEVER tighten a flywheel with an impact. It must torqued to spec by hand using a torque wrench. I have had them come in so fused to the crankshaft I had to cut them off when they didn't split.
     
     
    Clipper
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    Re: Briggs engine 2019/06/13 22:17:58 (permalink)
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    One thing I can’t understand is how it fires when the magnet is a quarter turn away from the coil. Well,it’s not quite a quarter turn, but close. Thr thing is it ran good until I took the flywheel off and put the impact wrench to it. The flywheel and key fit on the shaft just as they should. I did notice a very fine and hard to see hairline crack on the bottom of the flywheel. Could something move internally, like jumped a cog or two on the camshaft? Maybe a broken crankshaft? Thanks for the suggestions, but I m still at a loss to what is going on.
    Roy
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    Re: Briggs engine 2019/06/14 22:20:25 (permalink)
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    If you broke the crank internally the piston and valves would not move when you turn the flywheel. To check cam timing remove the valve cover and spark plug. Rotate the flywheel until the exhaust valve is closing as the intake opens, the piston should be at top dead center. I still don't understand how are determining that it is firing with the magnet a quarter turn from the coil.
    AVB
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    Re: Briggs engine 2019/06/15 06:59:47 (permalink)
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    With you Roy, I don't understand how it can firing a quarter off. Now even with the spark advance of 20 degrees it is delayed at start up closer to 0 degrees.
     
    Considering that this engine uses a magneto ignition system it is virtually impossible for it to fire a quarter turn off when the magnets are not crossing the coil's legs. It takes magnetic pulse for coil to generate the necessary voltage to arc the plug gap and it is the building and collapsing this magnetic field that induces necessary current in the primary winding that transfers to the secondary winding when it is suddenly collapsed by the coil internal triggering circuit.
    Clipper
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    Re: Briggs engine 2019/06/15 20:03:52 (permalink)
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    Going to try a different flywheel. I totally agree with what your saying. Everything checks out when I rotate the crankshaft. I will let you know in a few days if anything different happens.
    Clipper
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    Re: Briggs engine 2019/06/21 14:31:36 (permalink)
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    Tried a new flywheel today and does the same thing. Engine wants to kick back, like it’s firing too soon. When the engine does spin it fires and pops out of the carburetor every revolution, but this is hard on the starter because it’s firing too soon. I am stumped.
    Mikel1
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    Re: Briggs engine 2019/06/22 16:00:57 (permalink)
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    Why did you take flywheel off to begin with? How do you know it is firing too soon?
    Clipper
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    Re: Briggs engine 2019/06/23 21:18:46 (permalink)
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    Well Mike, here’s what happened. I bought this 19hp. Single cylinder lawn tractor from a fellow I know. The thing is only about three years old. It made a knocking noise when you started it and shut it off. Sounded loudest by the carburetor. I finally discovered that the plastic fan was loose and moving back and forth hitting the two 5/16th Allen head bolts that are there to use a puller on,because the two holes were egged out and making the noise. I figured out if I redrill the holes and tapped them to 3/8th I could fix it. Put the two 3/8 Allen head bolts in the flywheel, heated them up and pushed the fan down on them, melting the plastic making a very tight fit. I thought I should remove the flywheel and get the metal shavings out from under it. When I put the flywheel back on, being in a hurry, and like a fool slammed it home with impact wrench . Big mistake! Now just before the magnet gets to the coil it fires and either stops the starter or backfires out to the carburetor. It reminds me of a car engine that the timing is advanced to far and kicks back. About ready to junk the thing . P.S. someone told me it needed a flywheel, so I tried a new one. Did the same thing.
    post edited by Clipper - 2019/06/24 08:43:58
    Mikel1
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    Re: Briggs engine 2019/06/24 10:40:52 (permalink)
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    Stops the starter and backfires out the carb. Have you checked the valves clearances and operation?
    Clipper
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    Re: Briggs engine 2019/06/24 10:49:47 (permalink)
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    Checked the valves and set them both at .006. They seem to be working as they should. I know it was awful stupid of me to tighten it with an impact wrench, but I gotta wonder if internally the cam couldn’t have jumped a cog.
    Roy
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    Re: Briggs engine 2019/06/24 11:54:49 (permalink)
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    Read my second post regarding checking the cam timing.
    Clipper
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    Re: Briggs engine 2019/06/24 18:24:26 (permalink)
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    Do you set the valve clearance when they are open or closed? Is .006 for both about right?
    AVB
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    Re: Briggs engine 2019/06/24 18:45:36 (permalink)
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    Clipper
    Do you set the valve clearance when they are open or closed? Is .006 for both about right?

    Of course when they are closed otherwise you will not get the feeler gauge in the air gap. Exhaust valve is closest to the flywheel. The Briggs procedure is bring to TDC compression and continue to rotate until the piston is 1/4" down in the cylinder then adjust both valves.
     
    Intake Valve.003-.005 in (.08-.13 mm)
    Exhaust Valve.005-.007 in (.13-.18 mm)
    Clipper
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    Re: Briggs engine 2019/06/26 20:52:34 (permalink)
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    Set the valves per your instructions. When the flywheel gets to about 10:00 o’clock the starter can’t get it over the hump, but it fires when it is supposed to, and I believe it was all the while. If you pull the flywheel to or just past TDC so it has a full turn to get moving it will start and run good, but there is a noise in the internal part of the engine. I would like to thank everyone who racked their brains trying to set me straight. I really appreciated it very much! I am done with this headache and am going to sell it for parts or push it out to the back forty. Thanks again.
    Mikel1
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    Re: Briggs engine 2019/06/26 21:07:50 (permalink)
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    Could be a problem with the acr
    Clipper
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    Re: Briggs engine 2019/06/26 21:13:10 (permalink)
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    What is the acr?
    post edited by Clipper - 2019/06/26 21:14:22
    Mikel1
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    Re: Briggs engine 2019/06/26 21:16:16 (permalink)
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    Acr= automatic compression release
    Basically bleeds off compression to start up since they make weak starters
    Clipper
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    Re: Briggs engine 2019/06/26 21:20:16 (permalink)
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    I thought the starter may be weak, but the acr is new to me.
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