Motorcycle Repair: Starting problems after electrical short, using a multimeter, rectifier diodes

Question
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Followup To
Question -
Hi there,

I have recently fitted a top box with an integrated brakelight to a Hyosuung GF125.  Unfortunately I managed to short circuit the electrics using a multimeter while looking for the rear brake light +ve cable.

The main fuse blew and after replacement the bike refuses to start.  It will turn over but just won't fire.

After trying all the obvious stuff (kill switch position, petrol in tank), I replaced the CDI - thinking this was the only delicate component in the low voltage circuit which I could have fried - but it made no difference.

What should I try next?

Thanks in advance Mark

Best regards,

Michael
Answer -
Hi Michael,

I would back track from the blown fuse, to the component the meter leads shorted.

Remove the top box/brake light from the circuit and see if the engine will start.

Other than the above, I dunno what else to suggest. I'm not familiar with the MC.

Respectfully,
Mark Shively


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Mark,

Thanks for the quick answer!

I have tried to scan back from the fuse and test the components as best I can.  I am getting the same resistance reading off each of the 3 magneto coils so I presume they are ok, and there is a reading from the ignition coil - so hopefully it hasn't blown.

The only other part I can think of is the rectifier.  It is giving infinite resistance reading across all terminals.  I presume this is bad!

Would the symptoms described (engine turning on starter motor but NOT firing on starter OR kickstart) be consistent with a blown rectifier?

There is no spark at all - could a rectifer prevent the power getting through the HT circuit to the plug?

Thanks again Mark.

Best regards,

Michael

Answer
Michael,

To test the rectifier diodes, first measure continuity in one direction as you have, then flip meter leads and test in the other direction (switch polarity). You shoul have high resistance one way, and zero or little the other.

The rectifier may have a role in the high tension circuit. It depends on the design of the systems. Again, I'm not familiar with this MC. I would need to see the wiring diagram.

Measure ignition coil's primary and secondary windings for continuity.

Use my email address for further assistance...easier. mcso429@netzero.com

Mark