Mag trouble? John Deere b

Wes Verbal · Sep 17, 2015

Another post on my b, maybe someone can tell me,
My tractor ran fine up to the other day when it started to pop crack and then died. X X ! So I've took carb off clean ports and etc thinking might be the problem area. But does not seem to be it? So I started to play with mag to see if spark was good I ran piece of copper gauge in top hole rotated flywheel and had a strong bluish color flame strike..... Which is good. So moved down to number two cylinder hole in mag rotated flywheel and click the spark wS very very weak . /: so would this be the cause of the (condenser or coil )on the mag .?
The tractor would run but... A lot of rough idle and backfire ,popping ,cracking and what not ? This 1st I've had other than model 50 and didn't work around on it much ,not had it that long.

John T · Sep 17, 2015

The same coil and condenser and points fire BOTH plugs. There could be a cap and/or rotor problem causing one spark to be weaker then the other.

John T

BushogPapa · Sep 17, 2015

My experience on JD Model "B" tractors is that if they were running well and started what you mentioned (or did it when attempting to start), it well may be moisture inside the mag..

It may not even be enough to visibly see either..

Many times, after setting over-night in the field, they would take an hour to get started and sometimes we had to wait for the morning Sun to shine into the opened up Mag, to get them started..

A Mag-equipped tractor that has been setting a good while may well get moisture inside the Mag after the first couple of hours use, as the moisture is evaporated out of the crankcase..

Once every couple years, you should clean the Mag Points and wipe the Rotor and inside of the Mag Cap, to clean out any Carbon..

After all these years, I still have NO problem liking a Mag..you just may need to remember this..

I think Mag problems happen very seldom, if the above is taken to caution..

Ron..

BushogPapa · Sep 17, 2015

Always have a NEW set of Autolite #3116 Plugs handy, just in case your JD "gets Mad at ya"..as they can do once in a while..!!

Plugs can get fouled when you least expect it...

Ron..

teddy52food · Sep 17, 2015

I have a Wico C mag in that it doesn't show continuity from the rotor side to where the plug wire goes in. Spark has to jump through.

Wes Verbal · Sep 18, 2015

Yeah. I have been looking into mine ... When the tractor does start it will start up fun but after it starts to get easy at idle speed it's terrible rough and popping some backfire ? #%^ I took carb off gave good clean run through put it back on and still same old thing. So I'm for sure has to be in the mag area. This tractor set for 10 years in a barn never moved and I started to use it just about everyday and it might just need a good clean or maybe a condenser not really sure ? I'd like to get a wico C mag to put on it since that is what most 44 had on them then.

greenmech · Sep 18, 2015

Try a new condenser, and check for shaft play in the mag. Too much play will do strange things to the spark. Ron Mn

Wes Verbal · Sep 18, 2015

Yeah I did notice if I take hand and roll fan and look at slack play which is normal. But I can see the mag where points are have some play in it ?

Wes Verbal · Sep 19, 2015

Yeah I did notice if I take hand and roll fan and look at slack play which is normal. But I can see the mag where points are have some play in it ?

Mag trouble? John Deere b

Wes Verbal

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John T

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BushogPapa

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BushogPapa

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teddy52food

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Wes Verbal

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greenmech

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Wes Verbal

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Wes Verbal

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