Fault Finding - Technical Help


I Have No Spark

Check the battery has power, switch on headlamp; this should stay bright for one minute

The Fuse Keeps Blowing

Replace the fuse with a 21 watt indicator bulb.  As the electrical circuits are switched on the bulb will glow dimly, if a faulty circuit is connected the bulb will glow brightly. If the bulb glows bright with nothing switched on, remove wires from components in turn until the bulb goes out, the last one removed will be the area of the faulty circuit.

How Do I Check The Ignition Unit Has Power?

Using a powerful bulb and a voltmeter check the main power feed in to the ignition unit. This would be the wire from the ignition switch or kill switch. A 21 watt indicator bulb with wires attached makes a very good test lamp, a voltmeter can be attached in addition. With this connected between the frame and ignition feed wire, the lamp should glow brightly, if dim or varying try moving the fuse holder, wiring, handlebars, to locate and faulty connections. Also test between the feed wire and the wire used to ground or earth the system, as a poor earth connection can be most difficult to find. The bulb draws similar current to the ignition and is a more useful test than the voltmeter.

Most older MKIII ignition units will produce a spark when switching the ignition on or off, if this is so and sparks are produced on all cylinders then the ignition coils must be in good order. If one or more fail to spark a coil could be faulty.  On four cylinder machines try disconnecting one coil at a time, and switching on and off, checking for sparks. On other machines the coils are used singularly or connected in a chain in series.  One coil failing can stop sparking but if it becomes short circuit to its case the coils after it in the chain will stop working. It is possible that a working coil is shorting to the case, and stopping the other coils in the chain from working.  This is very common when a Lucas coil is over tightened in the metal clamp; the case becomes crushed and touches the windings inside. This can occur when the coil warms up. The Micro-MKIII, Micro-Digital and Micro-Power units all turn off when not being triggered, therefore it is best to carry out the next test as you may not always have a spark on turning on and off.

I Have Sparks On Switching On And Off But Not On Cranking

Disconnect the wires from the ignition box that go to the stator plate. With the ignition on, touch these two wires together, making and breaking should produce a spark at the spark plugs. If sparks are present then the ignition box is most likely to be in good order, if none are present the box is faulty. The only units that will not trigger in this way are the Kawasaki KH, Kawasaki S and Suzuki GT units. Check that the rotor magnets are running within the two metal pole pieces. On British machines, if necessary the rotor can be moved out slightly by placing a thin metal shim around the taper. The ignition will not fire if turned by hand at less than 200 RPM.

How Do I Check The Stator Plate?

A full visual check of the condition of the circuit board and coils looking for loose or broken parts. Check for signs of the rotor touching the solder connections.  Using a multi-meter check the resistance of each pickup coil and then the total resistance across the wires or terminals.  With the meter still connected, run your fingers round the coils, if the resistance changes there could be a broken winding inside.

Testing a T3 or KH250 Stator Plate
Testing a Stator Plate, Types Nt1a, SS4, Kh1a, Gs1a, Z900/1000, BMW1a, BBE04, XS650, Dt1a, BMW2a & BMW3a

How Do I Check The Rotor?

The magnets should just hold the weight of the rotor when placed against a piece of steel. Check the marking spots are the same way round.  All magnets should have a similar amount of strength.

I Have Sparks On Cranking But It Won't Fire

Check the stator wires do not change colour in the wiring loom, as swapping these will make the ignition fire over 50 degrees retarded.  With a digital system check you have suppressed plug caps fitted of approx. 5000 ohms.  If timing has just been done, don't forget that the timing angle on the camshaft is half of the crankshafts (i.e. on a 650 triumph full advance timing is 38 degrees crankshaft but is set at 19 degrees on the camshaft).

I Have Continuous Sparking Without Cranking The Engine

A poor battery with a battery charger connected or one or more bad cells.  A high resistance in the wiring circuit or earth return.  Check that the engine is earthed back to the frame and battery circuit. Plastic coated frames must have a good earth return to the engine case.  A wrong type of ignition coil with a very low primary resistance, this will draw a very high current and produce a large volt drop across the wiring. The unit will keep turning on and off generating a chain of sparks.

The Engine Runs Fast At Idle, Kicks Back on Starting

Poor fuse connection or wiring running low or variable voltage to the ignition.  As the alternator charges into the system with increasing speed the problem can clear.

The Engine Runs (Poor Starting) But Misfires

Poor ignition switch or bad connection vibrating on and off. Spark plug caps open circuit (suppressors broken up).

How Do I Maintain My Battery?

Conventional batteries

Regularly check the battery, terminals and acid level. If the level drops below the lower level top up with distilled water. Always charge the battery fully is it becomes discharged. When the battery is not in use keep it fully charged and the acid level up to the upper level. Batteries not in use should be checked once a month.

Maintenance free batteries

Even so called maintenance free batteries need to be maintained!

All batteries should be voltage checked once a month or more often if they are not in use as batteries discharge quickly especially if they are stood for long periods or the machine has an alarm fitted. If the battery voltage drops below 12.4 volts the battery needs charging, a fully charged battery will read 12.8 - 13.0 volts. If the battery reads 11.5 volts or less the battery is over discharged and the internal resistance may be too high to charge at a normal charge voltage.

Further Help

If you still can't find a solution from the information above and continue to experience problems please contact us:

Fax: 0044 (0)1622 730930
or Email: help@boyerbransden.com

Or you can return any Boyer Bransden parts for testing to:

Boyer Bransden Electronics Ltd,
Frindsbury House,
Cox Street,
ME14 3HE.

The cost of this service is £25 including return UK postage or £40 including worldwide return postage. Please enclose your full contact details and a brief description of the problems you are experiencing. You will not be charged for this service if your part is faulty and under warranty.

Tel. 0044 (0)1622 730 939
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