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AC B110 with very weak spark?

A

Aaron SEIA

Well-known Member
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.
AaronSEIA
 
Remove coil & take to local mower shop(s) and have them check in a coil tester same may be bad,you didn't say if coil orig or new replacement.If coil checks ok I would suspect either mega fire module bad or flywheel magnets weak,which is a common problem on many of the older briggs eng,you can try checking magnets by putting a flat screwdrive blade on magnets to see how strong they are,this is only a relative test & can be inaccurate,if coil checks ok after that either change mega fire unit or swap/replace flywheel.

Before you remove anything from eng,check that you have a good clean & tight eng ground connection for mega fire module,check connection with an ohmmeter between block & end of wire that connects to module.
 
As Joe suggested check those magnets for magnetism as they're overlooked a lot of times. Hal
 
Is this a Cast iron Briggs, and I see you say you have a megafire module (points eliminator) if so the problem may be reversed polarity of the magnets. The old Briggs cast iron engine don't work well with the megafire modules. Have you tried reversing the leads on the megafire module that may help with the flywheel polarity.
GB in MN
 
Had someone suggest doing that on the Simplicity forum. Odd part is, it ran perfect one week and had no spark the next. Will give it a shot though. Curious why yuou say the cast Briggs doesn't do well on the megafire? Everything I read before I bought it said they worked great. I've read some about a Nova setup that is better yet.
AaronSEIA
 
My experience with either the megafire or Nova modules is sometimes they work and other times not so good, I take it your engine has a starter generator, they will work better with that system, they do not work on engines with multiple magnets like the engines with a charging stator. I have found that points and condenser ignitions provide strong better spark than those modules, and the old cast iron B&S with the external points are very easy work on or they can be converted to battery ignition very easy and you then have excellent spark.
GB in MN
 
Thanks for the info. I did try flipping the wires with no change. Guess the next step is having someone test the coil. Really need a second one of these so I can play with 2 of them.
AaronSEIA
 
Megafire won't work on engines older than mid 80's if I remember correctly.If older the flywheel needs send back to briggs to be remagitized.The polaritey of the magnets needs changed
 
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