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cjallis 
Bronze Level
Joined: 13 Jun 2013
Location: Sheboygan
Points: 97
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 Topic: Allis B no spark
Posted: 08 Aug 2025 at 7:45pm |
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Got an issue with spark. Tractor has been sitting inside for 10 years. Rebuilt head, lots of new parts. Magneto did throw spark last time I ran it several years ago. I did clean the points. They were dirty. Any help to troubleshoot the issue would be great.
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steve(ill)
Orange Level Access
Joined: 11 Sep 2009
Location: illinois
Points: 89215
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Posted: 08 Aug 2025 at 7:52pm |
there may be a corrosion on the point that dont WIPE OFF.... you might want to use a very fine sand paper or point file to get more AGRESSIVE....
Once you guarantee the point is OK... the condenser next to it is suspect, then the COIL.
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Like them all, but love the "B"s.
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WF owner
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Joined: 12 May 2013
Location: Bombay NY
Points: 5083
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Posted: 09 Aug 2025 at 7:54am |
You said that you cleaned the points. Are you sure you got the gears timed correctly when you reassembled it?
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cjallis
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Joined: 13 Jun 2013
Location: Sheboygan
Points: 97
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Posted: 09 Aug 2025 at 6:12pm |
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It actually wasn't timed correctly but now it is. Points I cleaned with a brush.still nothing. Is there anyway to test with a meter at the coil?
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 89215
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Posted: 09 Aug 2025 at 6:34pm |
coils for mags are hard to test.. If it is the old BLACK TAR COIL, it might be suspect...If the coil is plastic coated and red or similar, i would clean the point more agressive ( i dont know how a brush could do it... i would use sand paper or a file) .... and change the condenser.... and make sure the point is not grounded, condenser not grounded, ground strap on the outside of mag insulated.
you can clamp the mag in a bench vise and put a couple wires and spark plugs on and ground them together... turn the mag IMPULSE with a pair of pliers and look for the spark... you can feel the spring WIND UP, then SNAP.. ??
Edited by steve(ill) - 09 Aug 2025 at 6:37pm
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Like them all, but love the "B"s.
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
Points: 1488
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Posted: 09 Aug 2025 at 7:25pm |
 cjallis wrote:
... Is there anyway to test with a meter at the coil? |
The secondary windings (high-tension side) of the coil will read somewhere between 5,000-10,000 ohms; if they read open (infinity) the coil is bad.
The primary side is more difficult, it will be about 0.5 ohms (that's 1/2 of an ohm). This requires a pretty good ohmmeter, and is not definitive even if it looks good.
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nella(Pa)
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Joined: 11 Sep 2009
Location: Allentown, Pa.
Points: 3137
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Posted: 10 Aug 2025 at 7:47am |
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I had a problem with my B mag and sent it to Steve @B&B custom circuits 937632559six. It work well after he fixed it.
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ac fleet
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Joined: 12 Jan 2014
Location: Arrowsmith, ILL
Points: 2337
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Posted: 10 Aug 2025 at 8:12am |
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had to put a battery dist on my B --- problem solved!! Mags are junk from the word go!!
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http://machinebuildersnetwork.com/
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Ttague39B
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Joined: 09 Aug 2025
Location: Tunkhannock PA
Points: 44
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Posted: 11 Aug 2025 at 8:11pm |
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On my allis B I had a rebuilt man, ran great for like a year, sat for a couple months then nothing, had to free up the impulse and took a condenser out of a old $5 mag I bought to rebuild put it in and throws better spark then ever.
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