How to test spark plug with multimeter to see if is it is good or bad

 Its a very easy but useful test to make sure your spark plug is ok , you may need to clean the electrode to ensure you get a good reading but all you then have to do is set meter to read ohms and measure from the spark plug cap end to the electrode tip , and then from end to body to make sure no leakage to earth.

Buy NGK spark plugs here i always use them

Get set up turn meter to ohms reading on dial and clean the electrode as below 

Test between end of spark plug where HT lead cap fits and the tip of electrode the reading is very low only 1.2 ohms 

on a dirty part of electrode the reading goes wild and eventually read 188.9 ohms so very bad and to avoid this clean electrode tip 

Next test from spark plug cap end to the body to make sure no earth leakage your meter should read OL which is a good reading as it signals no leakage to earth via the body.

See video of this process below 

Motorcycle electrics fuel injection components

On most modern motorbikes carbs are a thing of the past, and in replacement we have the fuel injection systems. The cdi will control both the fuel injection and ignition timing on these systems and uses sensors to time the exact time and duration of the spark and injection pulse.

You have sensors fitted on the bike that measure certain parameters these are and could differ depending on the manufacturer model and system used.

Input side

CTS coolant temperature sensor .

ACT engine air temperature sensor.

BARO read the barometric pressure at or above sea level to aid calculation of injection pulse.

TPS throttle position sensor obviously tell the cdi where your throttle is positioned .

MAP manifold pressure reading to held aid in calculation of the fuel to air mixture needed.

ECM engine management computer where all fuel and timing is controlled

CPS crack shaft position sensor or pick up coil 

Output side

Injectors - inject fuel into the engine via a timed pulse from ECM

IAC - idle air control valve the controls the tick over of the bike 

Ignition Coil - increases the 12v signal from the ECM to 10000 plus volts needed to produce spark

Fuel pump relay - this energises the pump to pressurise the fuel system

Battery testing and charging system quick test

I usually measure the voltage with my multimeter set to min - max and the turn the key over and test battery under one of the bikes main electrical load conditions when the starter motor is operating.

If the multimeter hits 10v or below on its minimum and 14.00v on its highest it proves the battery is good as the battery is to dropping below 10v under load and its reaching 14v on highest reading so it charging well too.

If you battery drops below 10v is probably time to replace it and it is not reaching 14v its only reaching 12.0v- 12.9v it shows the charging system is not functioning correctly.

see video below of me doing this on a car.

Motorcyle electrical testing tools

Test lights are excellent tools and a must for any trouble shooting.

Multimeters are another invaluable tool when working on any electrical circuits.

Power probe is a very good tool but more of a luxury but when you have one they can be very useful indeed. 

Noid light  these are useful for checking the operation of injector wiring and signal if the injector is getting a pulse to fire from the cdi or not and if the wiring is intact.

Jumper wires and pins are needed to help access wires and terminals with minimal fuss and damage to the loom.

Battery testers are useful but you could use multimeter and get a similar result without the extra costs involved.

Oscilloscopes are very useful for picking up glitches and injector faults and fault on sensors like pick up coils etc but they are veery expensive so not needed for DIY.

Soldering tools are excellent for making permanent reliable fixes in the wiring when repairing damage wires or replacing components.

Motorcycle Voltage drop testing

This is a very useful test to learn and is essential to fault finding on any electrical circuit.

When measuring resistance with a multimeter they only send out 1.5v and as such do not test a cable fully , doing volt drop testing uses the actual voltage of the supply so tests the cable fully and will easily detect internal damage or resistance within the cable.

In voltage drop testing you test one side of the cabling either positive or negative, and measure on a loaded circuit for example touch multimeter lead from positive of battery to starter motor positive post and measure the difference in voltage across the two pints this is the amount of volt drop on the cable. 

this need to be as low as possible it he millivolt range if its 1or 2v or more its a problem there is damage or a break in the cable creating a higher than normal resistance and using up some of the voltage.

This can be done for any circuit on both positive side and ground side of any load and will tell you if you have damage or high resistance to the cabling.

The ground side is the same test touch from negative terminal of battery to negative terminal of load device in the case of a starter it would be the metal body of starter as this is earth to ground via the engine, the reading on the ground side should be 0v as the load should use up all voltage on the circuit but it reality there will always be a little voltage due to cable and real world results.

Basic electrical terms and meanings

Just a few of the term used in this blog and short description of what is meant by it.

Ohms law is the relationship between Voltage Volt, Current Amps and Resistance OHM.

Voltage is the power of the supply and can be 6v 12v or even 240v in a home 

Current is the measurement of the amount of electricity a load is taking the larger the load the larger the current and also the larger the wiring needs to be.

Resistance is any restriction the electricity current has to face when travelling through the circuit and can be the wire and connection or terminal and the load itself will have a determined resistance than can be measured in ohms.

You need to know a little about these in order to understand how to fault find, its best to watch youtube videos and animations to understand this but its all relatively straight forward.

Three thing that make up a circuit

Power supply or supply side which is the 6v or 12v battery the cable running form the battery unto the load. 

The load what ever is using the elect is usually called the load and could be a battery the heater fan or a cdi.

Ground side is the earthed side of the load and all return cables to the negative of the battery.

Motorcycle crank no spark start ignition pick up coil cdi testing

Job i did recently shows some testing , some good tests in it but not the the best video. Ill do better later.

Buy handheld oscilloscope from here