Intermittant miss issue.

My Briggs & Stratton engines are from the 1980's &
I have found the Magnatron transistorised ignition is extremly
reliable, but have cleaned carburators every 5 years from crap &
getting a bit gumy. One them suffers from the zinc metal warping -
effecting tank seal.

I tested if it's the iginition by
Getting an old neon timing light and some clear tubing to allow a .166"
gap between the spark plug and tester electrode if it jumps that and
the engine runs (Remember a Magatron equiped unit requires min 250RPM
to spark)
If you think the cut off wire is shorting disconect it and fire it up
-you need a wooden broom handle handy to disconnect the spark plug boot
to kill the engine though after the test.

The Coil should measure 2500 - 5000 Ohm from spark plug lead to ground
No Ohm reading or much less than 2500 Ohm mean either lead or coil
replacment.

My ran and missed badly indication ignition issues, however the spark
was there ALL the time.

In My case the Engine had come to hard stop several times - as it's a
shredder and the FLYWHEEL KEY was partial sheared causing the timing to
be way off.
So unscrewing the starter clutch using a brass drift and then a 3
legged puller the sheared key was revealed.

After replacing the key with a new genuine B&S aluminium key all was
100%
The reason they are aluminium is to protect the crankshaft from a
sudden high speed stop by allowing the flywheel to shear the key rather
than twist the crank.

I really like B&S Engines except for there Pulsejet carburator with the
zinc warping issues. They do a lot of work between major services.
I was looking into Honda but after finding out you still need to decoke
them and they contain an internal timming belt I have lost  interest in
them at least with B&S you can get parts easly.

Hope this saves someone some time & money.