heres how to test the ignition.

remove the plug, place it on the belt adjuster so its body has a good earth

put a rag over the spark plug hole to collect any ejected fuel (make sure you can prevent or deal with a fire if you have one)

ensure the stop/run switch is set to 'run' (open circuited switch)

crank the engine - observe the spark should be regular and bright blue/white, not orange at all?

put ohmmeter(DMM) between earth and condenser terminal

if the points are open, the resistance of 2(+/- 20%) ohms  indicates the coil LT circuit is good

if the resistance does not fall below 2 ohms when the points close, then the points are faulty and need cleaning or replacement.This requires the special puller as a normal one will damage the coil.

unscrew ht cap, resistance of the cap should be 5k ohms or you will get VHF interference

Correct OE plug is Champion L86c / L86cc for perfect running, NGK have given me lots of problems!

resistance of the HT wire should be less than one ohm if you unscrew it

resistance of the HT to earth is 5k (+/- 50%) ohms, this indicates healthy HT side of the coil.

 the warning lamp wire can be taken off the dynastart regulator D+/61 terminal and used to test the resistance is low and charge up the condenser too.

the wire can first be made to some earth - the bulb lights(or you havent got the ignition on or mucked up), then touch the wire onto the condenser terminal for a second (this charges it up, and ensures you cant fry the coil LT with excessive current, as that is impeded by the bulb)

Condenser specifics. In order to properly test the condenser, the LT wire must first be unsoldered and ensure the points are open.

then a voltmeter should indicate a falling condenser terminal voltage (as it discharges through it) . a digital meter will fal from 12v to 0v in about 4 seconds but a moving coil meter pretty instantly

if you have a capacitance tester, the value should be 0.3 microfarads.

If you have a resistance meter, the insulation should be about 20M ohms (you will see this figure climb as the meter charges the condenser incidentally) Anything bekow 1M ohm suspect the insulation is too bad, clean away any grit on the top and retest or replace.

replacing the condenser requires removal of flywheel, backplate and HT lead/wiring, desoldering terminal, drift out  and in condensers, resolder, replace wiring, backplate and reset points, timing etc, so a major job really!

If you cant crank the engine over, or you suspect the magneto is duff, then you can still get a good ignition to spark as follows;

1.ensure the points are open

2. connect a test wire to 12 volts, either a thin 0.5mm^2 wire or

 a >5w bulb<21w  in series(to act as resistance) with a thicker wire

3 flash the test wire on and off the condenser terminal (connected to LT coil as normal)

this will cause a strong spark on the plug you can see.

Warning, dont connect 12V onto the condenser for more than a moment, because it may burn out the LT coil.

I accept no responsibility for damage caused by these tests, use them at your own risk.