allis b

Dblair · Jul 14, 2017

I'm new on this forum , I usually post in Oliver or Pulling . I bought a B with a mower on it last year and it started acting up . it misses a little when the temp get up and has no spark if you stop it for gas or what ever . it's probably the coil or condenser in the mag what are your experiences with this . thanks .

old · Jul 14, 2017

In a mag yep once hot and you loose spark most likely the be a bad coil. Condensers almost never go bad unless they start to leak

Dblair · Jul 14, 2017

thanks Old that's what I thought might be . I appreciate the conformation .

Traditional Farmer · Jul 14, 2017

I'd still replace the condenser 1st because its a whole lot cheaper.

old · Jul 14, 2017

Ah but a new condenser now days is a 50/50 chance of it being god/bad right out of the box. I do not replace condensers any more since I have had as many bad ones that where new as I have had good ones

Traditional Farmer · Jul 15, 2017

So what do you do if you have a bad one?

JOCCO · Jul 15, 2017

I will add: I have seen when engine gets warn if condecer is bad they start backfire. Some times they will start skipping and rounding rough like out of time. I have not seen as many bad condenser as old says but there are different types using correct one is important.

Dblair · Jul 15, 2017

thanks again guys . I bought a coil right here on this site and will put it in , I haven't bought a condenser yet . thanks everyone for their input .

JOCCO · Jul 15, 2017

If you are dealing with the magneto (depending on type) make sure the metal areas where it mounts are clean and check the wires and connections inside for corrosion.

old · Jul 15, 2017

Hope you luck out and get a good one. But in all my years of messing with engines I have yet to have a bad one. Condensers are pretty much like battery ignition coils if wired up correct they are almost bullet proof. Only time I have seen a battery ignition coil go bad was when it was 6 volts and hooked to 12 volts.
On mags the coil goes bad due to getting to hot to many times. Way back in the day Gravely had a recall on there machines due to the mag getting to hot so they figured out a way to ventilate them

old · Jul 15, 2017

A condenser is nothing more then a capacitor and having the correct MFD one of a higher MFD is the way to go if you can find that info that is.

tractorguy2 · Jul 15, 2017

I don't know how some of the members on this site get so many bad condensers. I buy and sell about 40 magnetos a year. I put new points and condenser in all of them. I've never had a bad new condenser in the last eight years.

I would suspect the coil is bad. Most Allis B tractors used the FM J4B3 magneto. They are known for bad coils. I would also put the points and condenser in it.

tractorguy2 · Jul 16, 2017

The coil on the FM magnetos is fastened with two slotted set screws in the top of the housing. You need to first clean all the dirt and carp out of the holes and screw slots. I use a tiny ball cutter and Dremel tool to clean the slots.

Most times the screws require heat to get them out. A good hot air gun or propane tourch will do it. Just heat the side of the housing where the screw is.

allis b

Dblair

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old

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Traditional Farmer

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old

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