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Briggs and Stratton 8B Weak Ignition


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  #1  
Old 10-20-2013, 03:27 PM
Zen Zen is offline
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Default Briggs and Stratton 8B Weak Ignition

I just pulled the Briggs 8B off my Snappin' Turtle mower to clean it up and get it going. Mechanically, it seems to be in very good condtion for its age but it has a very, very weak spark. With the plug out I can spin it over with my ratchet and it will shock me if I hold the wire, but it won't jump a spark across the plug. I am pretty sure that the coil is a big part of the problem. It looks like it has melted down. Is there a way to test the coil or should I just go ahead and replace it?
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  #2  
Old 10-20-2013, 06:09 PM
Ed Radtke Ed Radtke is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

clean points and replace condenser.
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  #3  
Old 10-20-2013, 06:16 PM
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John Newman, Jr. John Newman, Jr. is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

I would check, clean & gap the points and replace the condenser first. You may still have a good coil in spite of its appearance. Since you can still feel a bit of spark with it, I would hold off on replacing it untill you do the cheap & easy parts first.
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Old 10-20-2013, 06:30 PM
TekNik TekNik is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

yeah, check the points and condenser first.....
I've been there...I changed the coil on another briggs points engine when it was the points...
TekNik
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Old 10-20-2013, 06:48 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Once I got into it, the points are corroded and they didn't seem to be opening much. I took the points off and the pin that moves them is broken. The top half came out, but part of it is still down in the block. Any ideas on how to get it out?
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Old 10-20-2013, 07:16 PM
K-Tron K-Tron is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

When I rebuilt the 8R6 on my Eclipse reel mower last year, I used Briggs points 29667, condenser 391792 and coil 291617. I paid $55 for those three parts on ebay. It was well worth the expense. The machine has a very hot spark now and always starts in one pull.

Chris
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Old 10-20-2013, 08:17 PM
TekNik TekNik is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Zen,
you are talking about the plunger, right?
TekNik
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Old 10-20-2013, 08:27 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Quote:
Originally Posted by K-Tron View Post
When I rebuilt the 8R6 on my Eclipse reel mower last year, I used Briggs points 29667, condenser 391792 and coil 291617. I paid $55 for those three parts on ebay. It was well worth the expense. The machine has a very hot spark now and always starts in one pull.

Chris
I can only find one 291617 coil on eBay right now and it's at$69.99 with 3 days 19 hrs to go on the auction. It does have free shipping though. I've ordered a points and condencer set and a fiber plunger. I've got a feeling I'm going to still need a coil. This thing looks like someone built a fire under it. There was melted plastic from it in the bottom of the flywheel shroud. But, for 70+ bucks, I'll take a chance on having to tear it back down.

---------- Post added at 08:27 PM ---------- Previous post was at 08:24 PM ----------

Quote:
Originally Posted by TekNik View Post
Zen,
you are talking about the plunger, right?
TekNik
Yes. I didn't know what it was called, but I looked it up in my manual, and it's a fiber plunger #65704. I've got one ordered . . . but I've still got to get the broken part of the old one out.
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Old 10-20-2013, 08:45 PM
TekNik TekNik is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Zen,
I never had my 8B apart, a few pictures of the points location and plunger would be helpful.
Thanks
TekNik
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  #10  
Old 10-20-2013, 10:30 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

The first picture shows the points sitting in place. I have already removed the condenser. The second picture shows the plunger that the points rest on. The third picture is with the plunger removed (but the bottom half of it is still down in the hole). The last one shows the part of the plunger that I removed.
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  #11  
Old 10-20-2013, 10:34 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

This is from the manual. I marked the plunger and the location it goes in with red. The plunger should be shaped like a long dowel pin with a thin section in the middle. Mine has apparently broken in that thin section and what's left of the bottom half is still in the block.
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  #12  
Old 10-20-2013, 10:58 PM
TekNik TekNik is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Zen,
I've never had my 8B ( a future project, it runs too good to dig into) apart, but I'd think that if you would pull the crankshaft the broken bits will just fall out.
though you might be able to get it out without pulling the crankshaft using some picks and needles.
TekNik
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Old 10-21-2013, 09:24 AM
Mike Unwin Mike Unwin is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

That is strange about the melted coil,this summer I was working on a Briggs Model N and the was melted too.The material was on the the shroud and reformed I was thinking maybe some one had sprayed mine with something like "brake cleaner" I replaced the coil even though it was working.Very odd. Good luck Mike
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Old 10-21-2013, 02:27 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Quote:
Originally Posted by Mike Unwin View Post
That is strange about the melted coil,this summer I was working on a Briggs Model N and the was melted too.The material was on the the shroud and reformed I was thinking maybe some one had sprayed mine with something like "brake cleaner" I replaced the coil even though it was working.Very odd. Good luck Mike
I have no idea what could have caused this one to melt down either. There is no sign of the engine ever running hot enough to cause it to melt . . . and it's not like a 12 volt ignition system where you can leave the switch on with the points closed and cause it to overheat. If something shorted out internally, it looks like it would have shut down the engine long before the coil ever got hot enough to melt down like this. I haven't worked on very many small engine ignition systems, but I have worked on a lot of different automotive ignition systems . . . and I've never seen ANY coil melt down like this one did. It looks like someone roasted it over a fire. And considering the condition of the points and how little they were opening, I'm really suprised that the coil put out anything. So maybe someone did spray something on it that desolved it. I'm going to replace the points and condenser and the plunger and see what happens.
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Old 10-21-2013, 02:51 PM
TekNik TekNik is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Zen,
Have you had any luck getting the plunger out?
I thought of another way to get it out...
Just tip the engine onto its head.
the oil will need to be drained first though....
TekNik
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Old 10-21-2013, 02:55 PM
Power Power is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Coil probably has a few shorted turns.
Will still have enough voltage to create a spark and run engine, but shorted turns cause it to run hot - hence melted insulation.
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Old 10-28-2013, 10:05 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

I've been searching for a new Briggs and Stratton #291617 coil and can't locate one locally or on line. The only thing I'm finding is an aftermarket coil that comes without the "E Lamination." You are supposed to remove the old coil and slide this on the middle leg of the original lammination and it's held in place by a clip. Here's a link to the eBay auction for the part ( http://ebay.com/itm/Magneto-Coil-fits-Briggs-Stratton-point-type-engine-/231024135690 ). I've also found a coil like this on line in a couple of other places for about the same price. Has anyone here ever used one of these aftermarket coils?
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  #18  
Old 10-29-2013, 05:51 PM
Fifty7ChevyNut Fifty7ChevyNut is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Mr zen,
i have be playing with briggs engines for long time. I would wire wheel the laminations as good as possible, and lightly oil them. Use sandpaper or scotchbrite pads on flywheel magnets. Wire wheel, or wire brush will sap magnetic strenght. Gap magneto, points and plug to factory specs.

The plunger is a paint. I have had only one break in 40 years, and it was an absolute pain to get out. Ended up removing crank, and then still had to drill it out. Be very careful though.once you get a small hole in it, you can pick the rest out with carb or dental pick. There is a right and wrong way to instal the plunger. Wrong way and your points cover will get oil in it, and short out points.

I have about 800 engines, almost all are cast iron blocks, but i think the later iron engines share same coil as the early briggs engines.

I also have an early snapper with with cast snapper head on the front.

Don
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Old 10-29-2013, 11:49 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Thanks for advice. I order the replacement coil today. I still haven't gotten the broken part of the plunger out. I did manage to drill a small hole through it and have gotten a few bits and pieces out with a small pick, but there is a piece of it that just doesn't want to budge. I'm about ready to give up and go ahead and pull the crank out before I destroy something. I didn't want to, but I guess since I'm this far into it, I might as well just go all the way through the engine.

Quote:
Originally Posted by Fifty7ChevyNut View Post
Mr zen,
There is a right and wrong way to instal the plunger. Wrong way and your points cover will get oil in it, and short out points.
In the manual I have (scanned .pdf version) the plunger looks the same on both ends, but the new one I bought has a small groove near one end. Does that groove go up or down?
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Old 11-02-2013, 07:56 PM
Zen Zen is offline
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Default Re: Briggs and Stratton 8B Weak Ignition

Well, I got it apart and got the plunger out. I guess the bottom of it was mushroomed . . . it was easy to push out the bottom once the crank was out. Other than a little carbon build up on the top of the piston and in the combustion chamber, it looked almost new inside. I'll finish cleaning it up and start putting it back together tomorrow.

I found a video on youtube that said the small groove in the plunger goes up towards the points. Is that right?
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