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Author Topic: Weak Spark  (Read 7368 times)
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jaredvh
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« on: September 09, 2007, 04:58:55 PM »

I have a 18hp briggs opposed twin engine.  The spark seems to be really weak on one side.  What are some ways I can get a stronger spark?
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BriggsandStratton1218
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« Reply #1 on: September 09, 2007, 05:01:26 PM »

Try cleaning your armature and magnets.
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jaredvh
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« Reply #2 on: September 12, 2007, 09:29:01 PM »

I sanded down my flywheel a bit, how clean does it have to be?
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« Reply #2 on: September 12, 2007, 09:29:01 PM »

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mowerracer313
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« Reply #3 on: September 12, 2007, 11:07:49 PM »

I had the same problem on my grass cutter and the coil was shot,  put a new one on and problem was gone.
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BriggsandStratton1218
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« Reply #4 on: September 13, 2007, 02:42:17 PM »

I sanded down my flywheel a bit, how clean does it have to be?

Until its nice and shiny.
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Hotrodboy91
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« Reply #5 on: September 13, 2007, 06:32:04 PM »

The opposed twin briggs are well known for often needing a coil replacement. Most likely if you replaced this coil the problem would be solved.
Only other things to check are...

air gap between flywheel and armature. supposed to be set at 0.10gap
A business card works great for setting this gap.

Check flywheel magnets to make sure they are strong. There should be a strong pull against your screwdriver when you put it on the magnets.

Also its possible that your wire too the one cylinder could be grounding out at some point along its route through the shrouding and various shields (The wire could have been cut or nicked at some point when the engine was being re-assembled, causing it to ground out)

One thing that is not true in any way shape or form is the need to sand the flywheel magnets or armature legs down. IT MAKES NO DIFFERENCE!!!!!
The only thing the magnets and the armature care about for making the initial energy production through the magnets passing the armature is the proper air gap, nothing else.

-Casey
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BriggsandStratton1218
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« Reply #6 on: September 13, 2007, 06:44:42 PM »

Sanding of the magnets and armature is to remove any rust that can accumulate over time, which CAN effect spark strength.
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« Reply #7 on: September 13, 2007, 06:49:38 PM »

The opposed twin briggs are well known for often needing a coil replacement. Most likely if you replaced this coil the problem would be solved.
Only other things to check are...

air gap between flywheel and armature. supposed to be set at 0.10gap


-Casey

air gap between flywheel and armature. supposed to be set at .010 gap
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Hotrodboy91
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« Reply #8 on: September 13, 2007, 07:21:37 PM »

air gap between flywheel and armature. supposed to be set at .010 gap

oops! Sorry for the typo yes its supposed to be .010 !
Sorry if it caused anyconfusion!
-Casey
Sanding of the magnets and armature is to remove any rust that can accumulate over time, which CAN effect spark strength.

Sorry, but I have yet to see any FACTS supporting that.
The only reason you'd worry about the rust is if it was very thick, and caused a
problem in setting the proper air gap. Electricity does not cross between the flywheel and armature at any point and magnetism doesnt care about rust....

On the other hand, I HAVE read information strait from Briggs & Stratton specifically stating that it doesnt matter and sanding is useless.

Now, if you want to argue with various testing and research Briggs & Stratton has done be my guest!

-Casey
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hotrodmower16.5
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« Reply #9 on: September 13, 2007, 07:43:35 PM »

I am not arguing i am just going to give my two cents about the sanding the rust, I had some parts give to me and there was a coil, I seen some rust on it and did not think anything about because i had also read that rust does not matter well it does, Because i put it on my engine i was working on there was no spark so i did some sanding and then it started sparking and i used the same business card both times, I am still using the same coil today that was last year, Just my two cents.
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BriggsandStratton1218
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« Reply #10 on: September 13, 2007, 08:09:51 PM »


Sorry, but I have yet to see any FACTS supporting that.
The only reason you'd worry about the rust is if it was very thick, and caused a
problem in setting the proper air gap. Electricity does not cross between the flywheel and armature at any point and magnetism doesnt care about rust....


-Casey

You want facts?  Go do some work on small engines.  Rusty armatures, and rusty magnets will affect spark strength.  Magnets do not have full strength when they have to power through rust, not having full strength WILL cause weaker spark!!  Cleaning the magnets, dosnt nessicarily have to be  sanding, it can be a wire brush will remove the rust thus removing the "barrier" between armature arms and flywheel magnet.  Have you ever worked on points ignition systems?  If the points are dirty or have any corrosion on them, its basically the same principle, you get weak or no spark.  I had this problem last week on a 28ci.  Barely any spark, cleaned magnet and armature and bingo bright blue spark.  You say electricity dosnt pass through them, but a magnetic field does, which can be broken or disturbed, as I stated above.
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Hotrodboy91
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« Reply #11 on: September 13, 2007, 08:49:26 PM »

You want facts?  Go do some work on small engines.  Rusty armatures, and rusty magnets will affect spark strength.  Magnets do not have full strength when they have to power through rust, not having full strength WILL cause weaker spark!!  Cleaning the magnets, dosnt nessicarily have to be  sanding, it can be a wire brush will remove the rust thus removing the "barrier" between armature arms and flywheel magnet.  Have you ever worked on points ignition systems?  If the points are dirty or have any corrosion on them, its basically the same principle, you get weak or no spark.  I had this problem last week on a 28ci.  Barely any spark, cleaned magnet and armature and bingo bright blue spark.  You say electricity dosnt pass through them, but a magnetic field does, which can be broken or disturbed, as I stated above.

Well if you have test data and results i would be happy to see it!
And sorry, but unless you own your own small engine repair business and it is very large, I have much more experience than you do. Yes I have worked on points.
I have worked on some of the very first Briggs and Stratton engines, that had the entire ignition systems contained inside the flywheels (no points plunger) that were chain driven kick start, as well as everything in between up to brand new Briggs & Strattons. Heck, I've worked on engines that didnt even have electrical ignition.

First thing, is that with points, electricity actually passes through the points and the condenser. Electicity does not travel between flywheel and armature. Therefore, the given illustration is void. The typical amounts of rust between the flywheel and armature would not change the voltage produced. End of story.

Another thing is you say "bright blue spark" The color of the spark has nothing to do with the strength, voltage, or duration of the spark. This is another FACT strait from Briggs & Stratton research (as well as anyplace else that researched sparks) . The color is affected by many things such as the gap, the type of metal it is jumping between, and what is in the air the spark is traveling through to get to the other electrode.

Sorry about this to all you folks who arent in this.
But, it just really bugs me when somebody ensists something is true, but has nothing to back it up with. roll noplease confused

Happy building and racing!!
-Casey
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DANNY454
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« Reply #12 on: September 14, 2007, 03:38:27 AM »

Well if you have test data and results i would be happy to see it!
And sorry, but unless you own your own small engine repair business and it is very large, I have much more experience than you do. Yes I have worked on points.
I have worked on some of the very first Briggs and Stratton engines, that had the entire ignition systems contained inside the flywheels (no points plunger) that were chain driven kick start, as well as everything in between up to brand new Briggs & Strattons. Heck, I've worked on engines that didnt even have electrical ignition.

First thing, is that with points, electricity actually passes through the points and the condenser. Electicity does not travel between flywheel and armature. Therefore, the given illustration is void. The typical amounts of rust between the flywheel and armature would not change the voltage produced. End of story.

Another thing is you say "bright blue spark" The color of the spark has nothing to do with the strength, voltage, or duration of the spark. This is another FACT strait from Briggs & Stratton research (as well as anyplace else that researched sparks) . The color is affected by many things such as the gap, the type of metal it is jumping between, and what is in the air the spark is traveling through to get to the other electrode.

Sorry about this to all you folks who arent in this.
But, it just really bugs me when somebody ensists something is true, but has nothing to back it up with. roll noplease confused

Happy building and racing!!
-Casey

Sanding the flywheel magnets when they are rusty will make better spark strength. It happens a lot when engines sit a long time out side, the magnets get rusty thus causing weak spark. Thats why when that happens you have to clean them.

Sources...

3 years in a small engine repair business owned by my dad and self taught/schooled maintaining 4 lawn tractors + working at the shop.

   
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BriggsandStratton1218
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« Reply #13 on: September 14, 2007, 05:34:47 AM »

Thank You Danny!!!
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Hotrodboy91
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« Reply #14 on: September 14, 2007, 08:24:22 AM »

Sanding the flywheel magnets when they are rusty will make better spark strength. It happens a lot when engines sit a long time out side, the magnets get rusty thus causing weak spark. Thats why when that happens you have to clean them.

Sources...

3 years in a small engine repair business owned by my dad and self taught/schooled maintaining 4 lawn tractors + working at the shop.

   

Your not arguing with me anymore, you challenging research and testing conducted the leading small engine producer in the world. So, an entire companys research that has been around longer than you and your dad combined, your challenging with 3 years experience, fixing a few lawnmowers and maintaining your own? Your telling
them that their reserach is mistaken and that indeed, you have the right
answers? lol roll


To do the same research, you'd have to be a mechanical engineer that has been working for Briggs for years like the guys doing the tests are, along with using alot of special equipment. AND have a deep understanding of how things  work, far beyong just basic electricity and magnets....

-Casey
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