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  1. #1
    Limfe's Avatar
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    Engine backfires but won't start.

    I have a 1 1/2 year old craftsman with a 21hp briggs and stratton gold series plus engine. It turns over perfectly, I have plenty of spark and fuel. I believe the flywheel key is sheared. My concern withthe flywheel is the plastic cooling fins. Is there a specific way to remove them to get to the flywheel?

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  3. #2
    Limfe's Avatar
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    Re: Engine backfires but won't start.

    Flywheel is off. Used an impact wrench to remove the bolt so I wouldn"t have to wedge the fins or flywheel with anything. The pin didn't shear. Instead it craccked the top of the flywheel shaft. Any ideas on what would cause that?

  4. #3

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    Re: Engine backfires but won't start.

    Quote Originally Posted by Limfe View Post
    . Any ideas on what would cause that?
    Possibly when you removed the flywheel? How exactly did you remove the flywheel itself?
    After you removed the nut/bolt that holds the flywheel on, did the flywheel just lift off?

  5. #4
    Limfe's Avatar
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    Re: Engine backfires but won't start.

    I borrowed a flywheel puller but I didn't need to use it. The top of the flywheel was split so bad that I was able to lift the flywheel off with my hands.

  6. #5
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    Re: Engine backfires but won't start.

    Is there a chance that when "impacting" you may have tightened the flywheel more before breaking the nut loose?

  7. #6

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    Re: Engine backfires but won't start.

    Quote Originally Posted by Limfe View Post
    I borrowed a flywheel puller but I didn't need to use it. The top of the flywheel was split so bad that I was able to lift the flywheel off with my hands.
    Perhaps someone used a steel flywheel key instead of the aluminum one?

  8. #7

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    Re: Engine backfires but won't start.

    That took a really hard blow to split the flywheel or flywheel shaft (top of crankshaft?) like that. Could be over-tightening as aluminum won't stand up to it. Impact air gun would do it. I've seen tops of crankshafts mushroomed from hammering on them, even broken in two, but never split! On the other hand I've seen go cart racers tighten flywheels without the shear pin keys in them to advance time and they didn't crack them! Just have to get a lock washer to keep the wheel from turning. But in that case, if it did turn, what difference would it make since there is no flywheel key in it? Just re-set the timing position and try it again. I've never tried that but have friends who did.
    Last edited by DaveTN; 07-23-2013 at 12:36 AM. Reason: spelling

  9. #8
    Limfe's Avatar
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    Re: Engine backfires but won't start.

    I called Sears and they sent out a service technician 2 weeks later. He ordered a new flywheel and key.. He said if if I waited for him to come back it would be over a week and said when the parts were delivered I could install them myself if I wanted. Seemed simple enough. Apparently when the flywheel split it may have caused internal gears to jump out of time. I removed the oil pan and realigned the marks on the cam and drive shaft gears. Engine still backfires and will not run. Someone had suggested the valve settings. After inspecting the valves I found that the exhaust valve seat was split in two and briggs waranty only covers replacement of the whole head assembly. That's fine and dandy but I would liuke to know if that broken valve seat could have set this whole fiasco into motion????

  10. #9

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    Re: Engine backfires but won't start.

    Quote Originally Posted by Limfe View Post
    I called Sears and they sent out a service technician 2 weeks later. He ordered a new flywheel and key.. He said if if I waited for him to come back it would be over a week and said when the parts were delivered I could install them myself if I wanted. Seemed simple enough. Apparently when the flywheel split it may have caused internal gears to jump out of time. I removed the oil pan and realigned the marks on the cam and drive shaft gears. Engine still backfires and will not run. Someone had suggested the valve settings. After inspecting the valves I found that the exhaust valve seat was split in two and briggs waranty only covers replacement of the whole head assembly. That's fine and dandy but I would liuke to know if that broken valve seat could have set this whole fiasco into motion????
    Possibly so, but your messing with the engine so far would void any warranty.....

    As far as the cam/gears jumping out of time, I have to throw out the red "BULL" flag, and call the whole thread "bogus"?

    As far as removing the plastic fanwheel, that is obvious just by looking at it, why don't you post all of the engine's model, type, code numbers?

    Fish

  11. #10
    Limfe's Avatar
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    Re: Engine backfires but won't start.

    Quote Originally Posted by Fish View Post
    Possibly so, but your messing with the engine so far would void any warranty.....

    As far as the cam/gears jumping out of time, I have to throw out the red "BULL" flag, and call the whole thread "bogus"?

    As far as removing the plastic fanwheel, that is obvious just by looking at it, why don't you post all of the engine's model, type, code numbers?

    Fish
    The engine model number is 33187/0869 G5/111220ZA. The service tech stated to me that having me install the flywheel would not affect the warranty. Obviously the cooling fins were easily seen just by looking at it and I did not imply that any of the other issues had anything to do with it. The timing marks on the cam gear and the main gear were completely on opposite sides of each other. How or why this would happen, I have no idea. That would be why I asked on here.

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