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Hot!B&S 130202 5hp H will not fire.

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Rabon
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2019/04/14 16:32:16 (permalink)
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B&S 130202 5hp H will not fire.

My Father in law gave me an old '80 model tiller that he said ran but smoked bad when he parked it years ago. I figured rings were in order so I brought it home, tore it down and cleaned up all the carbon buildup. Other than the compression chamber the guts were in great shape. I lapped the valves back in, put on a new set of rings and popped it back together. No spark. I tinkered with the points a few times but couldn't get it to do anything even though they looked clean, the contact surfaces weren't worn badly and a tried a few gaps from 18 to 22. Gave up on that and put a Stenz electronic magneto on it. Now it sparks good, but still wont fire up. I don't have a compression gauge but it feels like it has decent compression. I pulled the carburetor back off of it and the bowl is full, so its cycling fuel ok. I tried a little carb spray directly into the intake with the carb off and still nothing. I don't know where else to turn so I'm hoping someone here has some advice.

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    Mikel1
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    Re: B&S 130202 5hp H will not fire. 2019/04/14 17:52:29 (permalink)
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    Did you check the valve clearances after lapping?
    Rabon
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    Re: B&S 130202 5hp H will not fire. 2019/04/14 18:16:06 (permalink)
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    No, I don't have narrow gauges but I figured it would be good since I didn't grind on them. If something like that could be my problem I'll pick up a set and check them just in case.
    Mikel1
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    Re: B&S 130202 5hp H will not fire. 2019/04/14 19:02:23 (permalink)
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    Yeah sometimes on the L heads the clearances can close up holding the valve open.
    Did you try another spark plug as well?
    Roy
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    Re: B&S 130202 5hp H will not fire. 2019/04/14 20:29:13 (permalink)
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    With the belt off, flip the flywheel backwards. If it bounces against compression it should be good to go. Also check that the cam is timed properly. The exhaust will close as the intake opens at TDC, if the piston is at any other position you need to correct it.
    Rabon
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    Re: B&S 130202 5hp H will not fire. 2019/04/15 17:34:32 (permalink)
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    Progress, the intake valve was indeed resting on the lifter. I pulled it in ground a little bit off to give it a .006 clearance. A few drops of gas in the spark plug hole and it backfired. So we're getting fire in a closed chamber. I put the carb and tank back on and tried it again but still nothing. Putting a little gas in the carburetor will get it to pop over four or five times but not crank. So now I'm assuming my problem is in the carburetor somewhere. I'm not a mechanic at all I just learn everything I can by doing.
    Mikel1
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    Re: B&S 130202 5hp H will not fire. 2019/04/15 22:46:23 (permalink)
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    So just a backfire when putting a little fuel in the cylinder and didn't try to startup temporarily? I wonder what the compression is
    Rabon
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    Re: B&S 130202 5hp H will not fire. 2019/04/16 19:38:05 (permalink)
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    Now I'm even more stumped. Borrowed a compression gauge and it's consistently 70-75 at 3 pulls, which several YouTube vids have claimed is normal for these engines.
    Rabon
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    Re: B&S 130202 5hp H will not fire. 2019/04/17 15:09:44 (permalink)
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    Something else I just thought of.
    When I pulled the head back off to correct the valve clearance, I noticed oil around the top of the cylinder. I assumed that since it hasn't ran, it hasn't heated up and seated the rings yet, so I didn't think it was important. However, now I'm wondering if I'm losing compression through the rings. I didn't hone the cylinder because it was in great shape and I didn't think I'd get it any better than that with a hone. So, is honing actually just for smoothing out the cylinder? Or do the micro-abrations from the stone help the rings to seat?

    Now I'm wondering if I should just start over. Did I screw up my new rings by dropping them into a cylinder that wasn't honed?
    AVB
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    Re: B&S 130202 5hp H will not fire. 2019/04/17 15:41:10 (permalink)
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    If thinking about using a flex or ball hone they only makes things worse. It takes a rigid hone to remove any oval and/or taper from the cylinder. Also since you installed rings thinking that would resolve a worn cylinder problem it will NOT. The cylinder must be honed and you probably will find that you just wasted your money on buying a standard of rings as it most likely will need to go to .020" over which requires a new piston and rings.
     
    As far as backfire was you referring out of the exhaust or the intake. If out of the intake it could very well be ignition timing . Since you using a ignitor and if it polarity can reverse that may be the problem as old cast iron engines used positive grounded ignitions. Modern today engines are using negative grounded ignitions.
    Rabon
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    Re: B&S 130202 5hp H will not fire. 2019/04/17 16:04:21 (permalink)
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    Nah I wasn't trying to fix a worn cylinder with new rings. The old rings were definitely the problem causing the smoking when I removed them I popped them into the cylinder to see the end gap and they were huge, like 3/16-1/4" each. The new ones are much tighter only like maybe .020 inches (I didn't have a feeler gauge when I installed them.) The cylinder itself was really smooth and there is no visible abnormality, scratches, or ovaling on it at all. That's why I didn't hone it. I don't own a hone and it looked so good I didn't want to spend the money if it wasn't necessary.

    The backfire thing sounded like it ignited as the exhaust valve opened producing a loud bang not muffled by being in a fully closed chamber. However I was pretty close to it so it may have been the intake. Either way, the timing marks are lined up and the flywheel key is not sheared so how could the timing be off?
    AVB
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    Re: B&S 130202 5hp H will not fire. 2019/04/17 21:27:34 (permalink)
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    Does this engine have a cast cylinder block?
    Rabon
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    Re: B&S 130202 5hp H will not fire. 2019/04/17 23:20:05 (permalink)
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    It's aluminum
    AVB
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    Re: B&S 130202 5hp H will not fire. 2019/04/18 05:59:29 (permalink)
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    I went reread you posts and if I not mistaken you said it will run a little bit will fuel added to intake. Is this correct? If so it might very be carburetor problems now as old fuel do mess them up by clogging metering passages. Try cleaning the carburetor and see that helps.
     
    Just information below.
     
    Okay. The electronic (Magnetron) coil usually works fine with these. The reason I ask if cast iron block is because those has the flywheel magnets reversed polarity which will throw the ignition timing way off. Just trying to figure why the ignition timing might be off. It sounds like it just ignited raw fuel in the exhaust as these engine do use wasted spark ignition system. This means they fire the plug on the beginning of the power stroke and during the exhaust stroke.
     
    I think you do have a cylinder problem but that probably just me having seen so many worn cylinders. I have never been able to eyeball one as it is hard for to see a .010 taper along with ovaling. I did one that fine at TDC but the BDC was off quite a bit. Actually tapered at .012 and the oval did finish cleaning up until .019. I was getting worried as I approach the .020 oversize. Even this one I couldn't see the problem with the cylinder as it looked fairly normal. Ovaling is easier to see as I back light the new rings and light will pass at the oval area. Normally you measure the cylinder at three levels (top, middle, and at the bottom of stroke) and twice at each level by one time 90 degrees of the other.
     
    And yes the compression is right it like should be with the ACR activate but you still might be losing bulk of the fuel load before or after the gauge reads the compression. The reason is because the gauge only registers the max pressure as it approaches TDC and not if it gets lost right afterwards it won't see the pressure drop. Normal operating (running) pressure is around 140 psi but with ACR doing its job at starting speeds it is not possible to read it.
     
    Its one of the reasons we use a leak down tester is it tells more about the cylinder top end as to if rings are holding their seal at TDC and if the valves are sealed along with if the cylinder head itself is sealed. Unlike OHV engines we can't use the leak down to test the rest of the stroke as we can't easily disable the valve train.
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