Briggs & Stratton Twin Cylinder L-Head Repair Manual page 17

1
Check Ignition
(With Electric Starter)
NOTE: Magnetron ignition system requires a
minimum of 350 RPM to produce spark.
With spark plugs installed, attach a #19368 ignition
tester to each spark plug lead and ground the other end
of the tester as shown in Fig. 8. Spin the flywheel
rapidly with engine starter. If spark jumps the tester
gaps, you may assume the ignition system is function-
ing satisfactorily.
WARNING: ON MAGNETRON equipped
engines, spark can still occur with a sheared
flywheel key. A severe shock or kickback
hazard may exist.
NOTE: Engines equipped with Magnetron igni-
tion system will still display spark at tester
with a partially or fully sheared flywheel
key. A partially sheared flywheel key will
affect ignition timing and engine perfor-
mance.
CYLINDER #2
Fig. 8 – Checking Spark
If spark does not occur look for –
1. Improperly operating interlock system
2. Sheared flywheel key (breaker points only)
3. Incorrect breaker point gap (when so equipped)
4. Dirty or burned breaker points (when so equipped)
5. Breaker plunger stuck or worn (when so equipped)
6. Shorted ground wire (when so equipped)
7. Shorted stop switch (when so equipped)
8. Condenser failure (breaker points only)
9. Incorrect armature air gap
10. Armature failure
11. Worn cam bearings and/or camshaft (breaker
points only)
Check Ignition
(Engine Running)
If engine runs but misses during operation, a quick
check to determine if ignition is or is not at fault can be
made by installing Tool #19368 ignition tester between
the spark plug lead and each spark plug, Fig. 9. With
the engine running, a spark miss will be readily
apparent. If spark jumps gap at ignition tester regularly,
and engine misses check for a fouled spark plug.
8
CYLINDER #1
IGNITION
TESTER
#19368
IGNITION
TESTER
#19368
ATTACH
TESTER
TO EACH PLUG
Fig. 9 – Running Check
Checking For Fouled Spark Plug
To check for a fouled spark plug or a non-functioning
cylinder, attach Tool #19368, ignition tester, between
the spark plug lead and each spark plug. With engine
running at top no load speed, ground one spark plug,
Fig. 10. The engine should continue to run on the other
cylinder. Repeat this test with the other cylinder. If the
engine will not continue to run when making this test,
the cylinder that is not grounded is not functioning
and/or the spark plug is fouled. Install a new spark plug
before proceeding. If miss continues, problem may be
carburetion or compression. See Cylinder Balance
Test.
IGNITION
TESTER
#19368
GROUND WITH
SCREWDRIVER
Fig. 10 – Checking for Fouled Plugs or Other Causes
Check Carburetion
Before making a carburetion check, be sure the fuel
tank has an ample supply of fresh, clean gasoline. Be
sure that the shut-off valve, when equipped, is open
and fuel flows freely through the fuel line. Inspect and
adjust the needle valves. Check to see that the choke
closes completely. If engine will not start, remove and
inspect the spark plugs.
If plugs are wet, look for –
1. Over-choking
2. Excessively rich fuel mixture
a. See Section 3 for adjustment procedure.
3. Water in fuel
4. Float needle valve stuck open