Motorcycle Repair: coil, honda c100, compression stroke

Question
I have a 1960s honda c100 can you tell me what the coil setting should read when tested. trying to find out if its bad, cant get bike started pit new battery spark plug , checked points, thanks

Answer
Hi Donita,


Check for cylinder compression before going too far.
You need some pressure to start the engine.
If the valve clearance is too tight it will
have no compression. The "T" mark is aligned
and the valves are set to .002" The engine
will be on compression stroke to make this adjustment.
If you feel some resistance to the kick starter then
the compression might be okay.

Lay the spark plug on the engine with
the plug wire attached and see if it has spark
when you kick start it. Try it without the plug cap too.

If you have no spark the most likely cause
is bad wiring or dirty, misadjusted contact points.

The points should be sanded clean and shiny if possible.
They should just break open when the "F" mark on the
flywheel aligns with the mark on the engine case.
They should also open to about .014" gap or else the
rubbing block that opens them may be worn down
and you need new points.

You can also check the coil wire for power
when you kick start it. Connect a multimeter
to the small coil wire and see if there is any voltage
when you kick it over. If not, the points, condensor
or magneto coil could be bad. The metal surfaces
on the coils under the flywheel could be rusty and
need cleaning. You will need a proper flywheel
puller to remove the flywheel. The flywheel key could be
sheared.

If you have a spark, try spraying some carb cleaner into
the carb opening and see if it fires.
Maybe the carb needs cleaning or the fuel is not getting to it
from the tank.

The ignition switch might be grounding out the ignition coil
try disconnecting it.

The ignition coil small wire primary is usually about
1-3 ohms to ground and the ohms on the plug wire is about 4800 ohms
without the cap. The plug cap is about 5000 ohms on it's own.

If you have compression, fuel and spark it should run.
Carb jets are very small and need to be clean.
Spark should be strong and blue colored.
Check all the ignition wiring for clean connections.

Luck!
Wayne S.

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