B & S Flywheel Magnets

Gunnar Storsveen

Forum Newbie
Joined
Sep 18, 2025
Threads
1
Messages
3
Briggs & Stratton Flywheel magnets:
Are there one or tree magnets and which POLE orientation?
See appended 2 files
 

Attachments

  • B and S_Flywheel Magnets.jpg
    B and S_Flywheel Magnets.jpg
    797.4 KB · Views: 2
  • Brigs and Stratton Magneto System.pdf
    29 KB · Views: 5
  • B and S_Flywheel Magnets.jpg
    B and S_Flywheel Magnets.jpg
    797.4 KB · Views: 2
  • Brigs and Stratton Magneto System.pdf
    29 KB · Views: 2

Auto Doc's

Lawn Addict
Top Poster Of Month
Joined
Sep 7, 2024
Threads
17
Messages
1,453
We need a picture of the flywheel for reference. There are different designs.

What engine number is the flywheel on?

If it is only for triggering the coil, I don't think pole direction is important. If it is the magnets attached to the underside inner portion of the flywheel then the poles have to alternate between N. & S. polarity.
 

Rivets

Lawn Royalty
Joined
Mar 11, 2012
Threads
62
Messages
15,690
Type this into your search engine and I’ll bet you’ll find the answer to all your questions. how do briggs ignition systems work diagram
 

Gunnar Storsveen

Forum Newbie
Joined
Sep 18, 2025
Threads
1
Messages
3
We need a picture of the flywheel for reference. There are different designs.

What engine number is the flywheel on?

If it is only for triggering the coil, I don't think pole direction is important. If it is the magnets attached to the underside inner portion of the flywheel then the poles have to alternate between N. & S. polarity.
I’ll find the engine number after the first weekend and may be open the engine. I am interrested in the MAGNETRON ignition system with two Darlington transistors. This ignition system made the B & S engines more reliable.
This summer I made a barn found:
42 years B & S Magnetron engine with generator: It fired after using the recoil som times.
👏👌😀
 

StarTech

Lawn Royalty
Joined
Feb 19, 2020
Threads
115
Messages
12,474
We need a picture of the flywheel for reference. There are different designs.

What engine number is the flywheel on?

If it is only for triggering the coil, I don't think pole direction is important. If it is the magnets attached to the underside inner portion of the flywheel then the poles have to alternate between N. & S. polarity.
Yes the polarity is important. That why some old point systems [cast iron blocks] will not work when converted; until, the magnets are re-polarized; otherwords, the North/South flipped. This because the cast iron point system used a positive ground vs the current negative ground system.

Opps showing my age...
 

Auto Doc's

Lawn Addict
Top Poster Of Month
Joined
Sep 7, 2024
Threads
17
Messages
1,453
Hi StarTech,

I had forgot the differences between coils because I rarely get anything with points anymore. Points ignition systems were just being phased out back when I was starting out many years ago.

I had also certainly forgot about the flywheel magnet polarity and correct coil mounting orientation.

Here is a video that I found online:
 

Gunnar Storsveen

Forum Newbie
Joined
Sep 18, 2025
Threads
1
Messages
3
Please see my appended drawing. Is the Magnet configuration Correct? Nice if you have comments either if the drawing is correct or not.
Regards
Gunnar
 

Attachments

  • Flywheel Magnet Configuration.jpg
    Flywheel Magnet Configuration.jpg
    613.8 KB · Views: 2

StarTech

Lawn Royalty
Joined
Feb 19, 2020
Threads
115
Messages
12,474
IF you have the flywheel at hand why use an old compass. Or have a non metal dish or plastic. Magnetize a small sewing needle, fill the container wit water, gently place the needle on water surface. Now if know generally which North the end that point North is the North end of the needle so note that. Now take the same and place near one of the magnets and the needle will tell you which pole it is.

Since I didn't have a compass here that what I use to setup my North to North swing of Cushcraft A4S beam antenna
 
Top