Help - Briggs 14 - No Spark (1949 Mayrath Engine)

[oliver2-44 10,810]

Briggs Model 14, Type 202020, Serial 50066

 

I haven't run my Mayrath in a few months, Started it up Saturday morning to get it read for a show this coming weekend.

Turned on the gas and it started on second pull of the rope.  Drove it to the driveway, shut it off, got something, cranked it up and drove down the block.

Went about about 2 blocks 2nd gear, and it died dead, no sputter, just dead.  checked for spark at the top of plug, none. A little hard to do on the street, so I bravely grabbed the lead and pulled the rope- nothing.

Pushed it home 2 blocks.

I've never been into the ignition on this tractor except to clean the points when I got it out of a shed.  It started right up with carb & choke tweaking. I've had it right at a year.

If it ain't broke, don't mess with those old parts I told myself.

So I soaked cover bolts and the crankshaft nut with penetrant for 2 days and gradually remove them. Thankfully they all came out, back and forth, back and forth

 

This is the manual for this engine. Unfornatualy it doesn't give any coil resistance ranges.

Model 14-domestic.pdf

 

 Model 14-domestic.pdf

 

Amazingly the flywheel pulled off fairly easy, jus some tension and a mild smak of a BFH.

Definitely needed cleaning, and the black asphalt varnish leaking out of the coil doesn't look good! 

Here's another pic of asphalt varnish down the side of the armature.

The manual says there should be a 0.004 ths air gap minimum. However the insulation is filling the air gap here.  but it is not grounding it out

varnish on backside of flywheel

Primary wire from coil attaches to this terminal , where a metal wrapped primary wire connects and goes to the points connection. 

Points and condenser in box on side of engine. The primary wire is on the right side of picture.

 

I took a bunch of resistance reading with my meter, but didn't find any smoking gun as to why it died.

Open  - Coil ground wire to core

0.6     - Coil ground wire to coil primary wire -So this reads across both coils one end to the other. it seems to me this should read open the the 2 coils being separated?

Open -  coil Primary lead to core

Open  - Spark plug lead to core

Open -  Spark plug lead to ground

9.1     - Coil primary to spark plug lead

Open - Primary wire to ground

0.2     -  Primary wire from end at terminal by coil to end at connection to points. 

Open - Primary terminal to ground

Open - Condenser lead to ground

Open - Points to ground

0.7    -  Resistance across closed points

12.8  -  Crankshaft to rotor - no insulation on drawing, so i think this is good

Open - Rotor to core

Open - Armature to core I am surprised this is open, it must be insulated by rust?

 

All help is greatly appreciated!

@953 nut Your always a good electrical guy, so I'm tagging you  

@oldiron613 i know you have several old Briggs on your Speedex, so I'm tagging you also

 

This is called Briggs Magna-Matic Ignition System.

 

 

 

Since I'm this far into this engine, I'm also going to lift the engine and replace the block to oil pan gasket and of course the head gasket.

I'm debating if I pull the carb and open the valve cove to check clearance.  

The engine runs good with about 1/4 choke, so carb could probable us a cleaning, but I hate to mess with an old Briggs carb that is working fairly well.

 

.

Pulling the front flywheel cover required several head bolts to be removed, so I pulled the rest to clean off any carbon. 

This is how it looked after just a wiping off, very little carbon

The head also has very little carbon.  That is a new plug I put in it to test if the plug was the issue.

Edited Tuesday at 06:22 PM by oliver2-44

[Handy Don 14,210]

55 minutes ago, oliver2-44 said:

The head also has very little carbon. 

I've seen more after cleaning!

I hope you’re able to resuscitate the old girl without a lot of trouble!

 

To me, if in ohms, this is surprisingly high. This equates to 8 watts. I’d expect a reading less than 0.01Ω

0.7    -  Resistance across closed points

 

This, too, I’d expect to be near zero.

 

0.2     -  Primary wire from end at terminal by coil to end at connection to points. 

Edited Tuesday at 01:22 AM by Handy Don

[oliver2-44 10,810]

Thanks Don, I’ll recheck those tomorrow and look for issues.  

[Achto 29,479]

Finding parts for those ignitions can be difficult. If worse comes to worse you can switch to a battery ignition. Add an internal resistor coil, hook it up to the points, & find a place to hide a battery. A small trailer breakaway battery will work. Some of the guys that I pull with use a Milwaukee drill battery to power the ignition on their tractors.

 

Much easier to pull off and hide on a tractor that has some sheet metal but some creative placement can help hide the up grade.

[oliver2-44 10,810]

13 hours ago, Handy Don said:

I've seen more after cleaning!

I hope you’re able to resuscitate the old girl without a lot of trouble!

 

To me, if in ohms, this is surprisingly high. This equates to 8 watts. I’d expect a reading less than 0.01Ω

0.7    -  Resistance across closed points

 

This, too, I’d expect to be near zero.

 

 

0.2     -  Primary wire from end at terminal by coil to end at connection to points. 

I cleaned the point sawing heavy brown paper then dialectic spray. They now measure .02 to 0.  

The primary wire may have some strands broken in it. It changes .5 to 0 as I wiggle it. So I’ll replace it. 
 

Any thoughts on the “9.1 coil primary to spark plug lead”. 

Edited Tuesday at 03:01 PM by oliver2-44

[oliver2-44 10,810]

I found an NOS coil on evilBay $46, points, condenser armored lead and gasket set.  It all rounds up to about $120.

[953 nut 60,592]

5 hours ago, oliver2-44 said:

I found an NOS coil on evilBay $46, points, condenser armored lead and gasket set.  It all rounds up to about $120.

Sounds like a good plan.