Briggd Engine giving me fits!

TimWafer · Apr 6, 2017

I have an old BRIGGS L-head engine that's driving me nuts. Its a model 233431 and has the points mounted on the side. Its on an old generator I seldom use.
A couple years ago I put a new coil, points & condenser in it as it had no spark at all. All was well and it ran fine afterwards. Maybe used it once or twice since then and still all was well.
Went to start it a week or so ago and back to no spark. Cleaned the points and new plug, still nothing. Suspected condenser but didn't have one. I did have a couple magnatron coils that don't require points so thought I would convert it over to that. Simple enough I thought. Both coils worked fine on another engine. I can only get a very very weak spark with them on this engine. Not enough to start or run even spinning it fast with a big drill. Magnet in flywheel seems strong. Coil is facing right way. Tried numerous plugs. What am I missing?
Tim

Geo-TH,In · Apr 6, 2017

I would use a wire brush on drill and
clean all rust off flywheel.

Then I use 3 one dollar bills as a spacer
between magnets and coil. That seems to
work well for me.

Try it and post back.

TimWafer · Apr 6, 2017

I did clean the magnet & flywheel up with emory cloth. Set the air gap to .010 and checked with an actual feeler gauge. The spark is so weak you cant see it unless the lights are off in the shop.

TimWafer · Apr 6, 2017

I just found a discussion on the web of this exact same problem with this exact same engine. From reading through the long discussion, the general consensus seemed to be that this engine for some reason has reverse polarity in the flywheel magnet and will not work with a magnatron coil. I have to go back to the original points & condenser or have Briggs reverse the polarity of the magnet for me. Anyone ever heard of this before???
Tim

Bob · Apr 6, 2017

"I have to go back to the original points & condenser or have Briggs reverse the polarity of the magnet for me. Anyone ever heard of this before???"

Yes.

I have an old 12HP like that, and used an "ATOM" ignition module successfully with it. They connected with two wires and if they didn't work on a specific engine usually they did when you reversed the leads.

NOT sure what's out there now, as "ATOM" apparently quit manufacturing them in 2005.

<img src = "http://www.electro-tech-online.com/attachments/atom-ign-mod-4-jpg.74323/">
INFO

ss55 · Apr 6, 2017

Twenty some years ago I replaced the points and condensers in my small engines with electronic pickups. They worked well for me. I don't know if those kits are still available.

TimWafer · Apr 6, 2017

Thanks!
I found someone who still has some "ATOM" modules available but they are no longer made. Also saw on Ebay a "Nova II" module that sounds like it may be the same idea. Think Ill give one or the other a try.

Delawaresurfman · Apr 6, 2017

Most times it's the points. Condensers rarely go
bad, although I replace them as a set. It's a myth
about sanding the flywheel. It's magnetic. It's all
explained on a Briggs web page. Spinning at a fast
rate, as you have done is very important to create
spark in these units. Another possibility is that the
keyway has very slightly sheared. This will have it
out of time. Another possibility as you have
mentioned is a weak magnet, this can happen but
very rarely. Reversed polarity I don't see how if it
ran when parked,

guido · Apr 6, 2017

Hello TimWafer,

Points are dirty. Draw a white piece of paper between them until it comes out clean. Then reset the gap,

Guido.

guido · Apr 6, 2017

Hello TimWafer,

010? Sounds way too tight. Try .018- 020. Also check the armature gap 006 or 008,

Guido.

guido · Apr 6, 2017

Hello againg,

018 to 020 is the points gap. Adjust the air gap 006 to 008. 010 is for electronic IGNITION!

Guido.

TimWafer · Apr 6, 2017

Believe me, I cleaned the points several times as you say and they are almost as new anyways. So is the condenser & coil. They were all replaced at same time and I doubt if there is 2 hours run time on any of them. I think either the coil or condenser went bad again. I am now leaning more towards the coil being bad as there was no spark at all.
I tried eliminating the points by using a magnatron coil. Actually tried 2 different ones. I could get only the very weakest of a spark.
According to the info in the discussion I just read, a few old Briggs engines used a flywheel magnet with reverse polarity and my 233431 is one of them. they would work with the original coil and points but not with a modern magnatron coil.
I'm going to get another original style coil and try one of the mentioned ATOM modules. I left the original points and condenser intact as they are mounted on the side of the engine. I just disconnected them. I think I might try them with a new coil before trying the ATOM. Just like to know what really was the original problem. At first I was sure it was just dirty points.

TimWafer · Apr 6, 2017

I meant air gap on the coil as points are not in use with the magnatron coil and .010 is for the electronic coil.

Fritz Maurer · Apr 6, 2017

The model 23 has a three-legged armature and a Magnetron unit has two legs. The magnet spacing on the flywheel for the original armature is not compatible with a two legged armature, points or electronic.

Hendrik · Apr 7, 2017

Did you check all your electrical connections for good contact, including grounds and those in the high voltage circuit?
HTH

TimWafer · Apr 7, 2017

On this engine the original points coil was two legged as is the magnatron.

TimWafer · Apr 7, 2017

Yep, everything was clean & bright. I might add that even though this engine is around 50 years old its amazingly clean and low hour. Mostly it just sits except for the occasional start up to test it. Maybe every couple years it gets run for a few hours.

TimWafer · Apr 7, 2017

By the way, I'm reasonable sure I can get it to run on points again with little trouble. My real question is why couldn't I get it to run on the magnatron coil. I always thought that was kinda a foolproof solution in most cases. The best answer I found was this engine was made with a reverse polarity flywheel magnet. I just never heard of that before. From what i read it was not common even back then but this engine had it for some unknown reason.
Tim

Wayne in MN · Apr 7, 2017

Remove the coil and remove any rust between the coil and engine mount.
With flywheel magnet not near coil, move coil .015" or more away from flywheel and tighten hold down screws. (is the coil ground wire under one of the screws?)
Rotate the flywheel so magnet is in line with coil, place .008" feeler gauge in between and then loosen hold down screws allowing magnet to set the air gap.
Remove feeler gauge by rotating the flywheel.
Set points gap to .020" maximum opening and test for spark.

gears · Apr 7, 2017

Tim, I've got that same issue on my big 16hp briggs, believe its the same model as you're working on but I'm not leaving this chair to dig around in the barn to verify

What I found was the polarity of that flywheel was opposite of the magnetron units, heard tell that you could ship the FW back to briggs and they'd re-polarize-magnetize it to work with a magnetron module or coil.

I tried one of the 2 wire splice on modules like that Atom unit (napa sells one) got great spark but it was too out of time to run.

I ran a battery automotive style ignition to it. 12v coil with power from the ign switch and ground it through the points. Runs great (until the points get oil on them).

Briggd Engine giving me fits!

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