Hmm, my tractor isn't getting spark anymore...

[dart451]

Went to start my old twin cylinder briggs 422707-1516-01...it went to start and then quit trying. Turns over great, won't even ignite with starter fluid. Checked for spark at plug wires, nothing! I checked the red wire from the key to the two wire plug going to the engine...when I turn key on, I'm getting good voltage. So, if I'm getting voltage, I shouldn't have a safety switch problem, right? Besides, it won't even turn over at all unless I have the left pedal fully depressed. Looks like I need to pull the flywheel...any other suggestions?

[KE4AVB]

Disconnect the kill wire at coil and test. If still no fire then disconnect one spark plug at a time while the other plug wire is still in place and test. Reverse this and check again. If you fire with plug wire disconnected you a have shorted plug; otherwise, the ignition coil is bad.

[Arkie]

Disconnect the kill wire at coil and test. If still no fire then disconnect one spark plug at a time while the other plug wire is still in place and test. Reverse this and check again. If you fire with plug wire disconnected you a have shorted plug; otherwise, the ignition coil is bad.

You can find that ignition coil (magneto for less than $20.

No need to pull the flywheel, the coil is mounted on the outside of the flywheel. Just pay attention on the new mag and install with the very faint letters THIS SIDE UP. Set the air gap with a credit card. Be careful and do not twist off the mag mounting screws. Gently peck on the 5/16 head of the screw before trying to remove if all is rusted up. Steel screw going into aluminum. Use little bit of anti-seize when going back.

I've had good luck using the $15 mags on them old Briggs twins.

You can download a free service manual for that engine.

Like KE4AVB says or hints, sometimes new correct spark plugs will make them old Briggs twin come alive for awhile.

[38racing]

I have a 1984 42.... Hadn't run in at least year. gas tank was empty. added gas. installed battery and used a booster on it too. A few shots of carb cleaner to get pump working and in a minute she was purring like a kitten. IIRC I replaced the coil on it a number of years back. Is it the opposed twin that I read you should not run with a plug wire off unless it's grounded ?

[bgsengine]

. Is it the opposed twin that I read you should not run with a plug wire off unless it's grounded ?

No- That'd be Onan. Briggs is polar opposite - both plugs fire at the same time, they are on same circuit, but a shorted plug can cause no spark on the other side (path of least resistance and all that).... some onan twin ignitions the secondary (high tension) circuit is grounded through each other, needs the other side grounded to fire the testing side... they've been known to experience damage by trying to run them with a plug wire off one side, (since the path of least resistance is then wherever there happens to be any weakness in the coil's internal insulation) and can't do a power balance test on these by removing plug wires.

[dart451]

Ok, disconnected the kill switch wire, no fire. Disconnected the left spark plug wire, no spark. Disconnected the right plug wire, no spark. So, I believe my magneto is bad...

[dart451]

Disconnect the kill wire at coil and test. If still no fire then disconnect one spark plug at a time while the other plug wire is still in place and test. Reverse this and check again. If you fire with plug wire disconnected you a have shorted plug; otherwise, the ignition coil is bad.

You can find that ignition coil (magneto for less than $20.

No need to pull the flywheel, the coil is mounted on the outside of the flywheel. Just pay attention on the new mag and install with the very faint letters THIS SIDE UP. Set the air gap with a credit card. Be careful and do not twist off the mag mounting screws. Gently peck on the 5/16 head of the screw before trying to remove if all is rusted up. Steel screw going into aluminum. Use little bit of anti-seize when going back.

I've had good luck using the $15 mags on them old Briggs twins.

You can download a free service manual for that engine.

Like KE4AVB says or hints, sometimes new correct spark plugs will make them old Briggs twin come alive for awhile.

Arkie, isn't a credit card a tad too thick? What is meant by pecking the 5/16 bolt? Thanks.

[KE4AVB]

Disconnect the kill wire at coil and test. If still no fire then disconnect one spark plug at a time while the other plug wire is still in place and test. Reverse this and check again. If you fire with plug wire disconnected you a have shorted plug; otherwise, the ignition coil is bad.

You can find that ignition coil (magneto for less than $20.

No need to pull the flywheel, the coil is mounted on the outside of the flywheel. Just pay attention on the new mag and install with the very faint letters THIS SIDE UP. Set the air gap with a credit card. Be careful and do not twist off the mag mounting screws. Gently peck on the 5/16 head of the screw before trying to remove if all is rusted up. Steel screw going into aluminum. Use little bit of anti-seize when going back.

I've had good luck using the $15 mags on them old Briggs twins.

You can download a free service manual for that engine.

Like KE4AVB says or hints, sometimes new correct spark plugs will make them old Briggs twin come alive for awhile.

Arkie, isn't a credit card a tad too thick? What is meant by pecking the 5/16 bolt? Thanks.

What Arkie is saying to do is called shocking the threads and head of the screw. I do it a lot of on Phillips (cross point) screws to loose them up where they semi seized. Most hex head you take a flat end punch and using a hammer hitting the punch to release seizure. With Phillips screws you use a solid same size point bit and hammer. Especially useful on the those Nikki Phillips bowl screws. Definitely keep you destroying the heads. Just to use common sense and don't go at it with a sledge hammer.

On the air gap I use a business card or repair tag stock to get the .010-.012 clearance. THe old way I use to do was a folded paper grocery sack but they are nearly impossible to find now that plastic has taken over. Plus do you want to risk destroying your credit card; though, I have threaten to get rid of mine a few times.

[bluemower]

Good comments from the others. Here is a little more info. Magneto coils seldom fail. The two most likely causes of failure are:

(1) the key switch fails and introduces battery voltage into the magneto shutoff wire. This burns out the internal winding in the coil. If this has occurred, failure of a replacement magneto coil is likely.

(2) corrosion forms on the coil mounting post, steel coil laminations, and mounting screws. In this event, the coil is no longer grounded - thus no ignition and no spark. If this has happen, remove the coil. Use a drill motor with a wire brush to clean up. Install and Recheck for ignition. This effort only requires a few minutes and does not cost anything to check.