Scotts Riding Mower 20hp briggs Cranks but Wont Fire

dj69firebird

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I just picked this lawnmower up for a very good price. The motor blew on my old mower and I do not have one to mow the grass yet so I need this thing fixed ASAP. It is a Scotts brand made by John Deere. It has a 20hp Briggs and Stratton motor. It is cranking over but will not fire up. I checked for spark and I have spark on one cylinder but not the other. I believe its the coil but I know that this thing has some safety switches and I am not sure if that has anything to do with it because I have noticed that it will not crank unless I push down on the brake real hard and sometimes I have to sit on the seat right. If there is anyone that has experience with this any help would be greatly appreciated. Also if it is the coil does anyone know where I can get one for a good price? Thank You
 

Arwing64

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The safety switches will prevent the engine from cranking and cut off ignition to the coils.

There is a wire that connects to both ignition coils that are there to shut the engine off. On the V-twins, there are a set of diodes in the wire which could have gone bad. That would cause one of the coils to fire and the other to not. If both diodes were bad, there wouldn't be any spark out of either cylinder since it would be shorted out.
The wire would have to be replaced. I don't think they are very expensive.

A good way to test it is to disconnect the wires from the coils and turn the engine over to see if they both have spark.
If both have spark, the wire is bad.
But if one doesn't spark, the coil is bad.

But before you replace the coil, measure the clearance between the flywheel and the coils and make sure they are correct. Common armature gaps are .006 - .010" and .010" - .014".
If it still isn't working, replace the coil. They aren't that expensive.
 
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