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B110 very weak spark?


B110guy

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Finally got around to working on my B110 with no spark. Have it set up on the bench with a battery so I can spin her over. No spark through the plug but have a very weak spark at the plug holder. I'm talking maybe 1/32" or so. Coil gap is .010 or a tick bit more, but not over .012. Any idea what the problem might be? Running a Megafire and coil with less than 20 hours of run time on them. Connections are all tight and polished.

B110guy

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Check your flywheel magnetism level. Occasionally the magnetism can dissipate or be of the wrong polarity to fire an electronic module. To have it set by Briggs to modern force and polarity is only the cost of shipping(free service/labor) if needed. I sent one out and it was a night and day improvement(like 1/4 inch gap spark).

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How can I tell if I have good magnetism? Is there a simple test I can do to see if it's good enough? Seemed pretty strong with my feeler gauge and sucked the coil right down when I loosened it. Does having even a weak spark rule out the megafire? I'm inclined to think it's the coil, as I went cheap and this was a sudden thing, just wouldn't start one day. Is there a quality difference between genuine Briggs and the aftermarket coils?

B110guy

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I can try that. It ran perfect one week, went to use it a week later and no spark. I need to buy another one so I have a backup :D

B110guy

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powerking_one

Aaron,

I would check the flywheel key (aluminum) as this a frequent cause of ignition problems. Any signs of wear/shearing and it will cause these kinds of issues. If you still have the points/condenser setup for the engine, consider switching back the system as a troubleshooting step. I tried one of the Mega-Fire modules on my brother's 16HP Briggs and to me, the spark looked "weak" compared to the points/condenser setup.

I would seriouly doubt the flywheel magnets being weak causing a step change in what was a running engine the week earlier(IMHO).

Tom (PK)

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The reason I mentioned the magnetism is the switch to electronic trigger. The original coil/condenser system has different sensitivites and tolerances vs the relative "absolutes" of a trigger, which has a threshold.

The test I used for verifying magnetism level was to use a socket wrench socket and a 1/16" inch piece of wood. There is likely a more precise way to do it, but that was what I had determined to be the level of a comparable known good modern flywheel. If it can still magnet through that it should be fine on the force level. That does not indicate polarity, which is also a requirement of electronic but not in condenser/points.

TBH, if you already have it out and open I would reccomend a true Briggs style magnetron module conversion. When I changed from points to Megafire it worked, but it was not what I would call impressive. Going to Magnetron was night and day, for a very comparable price.

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