SOHC.co.uk Forums > CB500/550
Cb550f blowing main fuse
TrickyMicky:
--- Quote from: Otis on August 18, 2026, 07:38:32 PM ---
--- Quote from: Bryanj on August 18, 2026, 04:54:16 PM ---If the black from the loom touched anything metal that would blow your fuse as black wires are 12v positive when key is turned on
--- End quote ---
The offending black wire that almost certainly has to be the culprit.
Just as an aside, I purchased a repro winker relay from David Silver for £18.50 delivered whereas they wanted £51.50 for a genuine part, the differential being just too far apart.
--- End quote ---
For what it's worth, I have fitted the (hopefully!) attached digital flasher unit to both my 400 and GB250. It will operate with either filament or LED bulbs, or even a mix of the two, the flash rate remains the same. Like yourself, the initial reason for this being an original OE flasher for the GB250 was only available from Japan at £112 plus carriage. The only downside I have found so far being if a bulb fails, the unit just carries on regarldless at the same flash rate. I found that it fitted into the rubber mount on the 400 quite qell.
Otis:
OK, I am now completely stumped.
With the help of you fantastic guys I have rectified all of the problems I had. I found a broken black wire from my footbrake cable and repaired it. I discovered a problem with my indicator flasher unit so ordered a new one which arrived today. I replaced my 30 amp main fuse with a 15 Amp as per your good advice. I put everything back together and before installing the new flasher unit I ran a check. Apart from the RHS flasher not working everything was as expected. Whilst she was idling nicely, I disconnected the old flasher unit and installed the new one only to find that the bike immediately stalled.
I realised straight away that something had gone but found that the fuse was still intact. I now have absolutely no idea what I have caused but the fuse is fine but there is absolutely no life whatsoever in anything although the battery is still reading 13 Volts.
Any thoughts please because if it's not the fuse then I haven't got a clue what to do.
Bryanj:
Check the voltage both sides of the fuse then at red wire of switch when turned off then black wire of switch tirned on.
What you are doing is checking for 12v at every junction point from battery onwards, wouldnt be first time a wire got accidentaly unplugged or a damaged wire, or switch, coincidentaly gave up
Otis:
--- Quote from: Bryanj on August 21, 2026, 03:35:30 PM ---Check the voltage both sides of the fuse then at red wire of switch when turned off then black wire of switch tirned on.
What you are doing is checking for 12v at every junction point from battery onwards, wouldnt be first time a wire got accidentaly unplugged or a damaged wire, or switch, coincidentaly gave up
--- End quote ---
Bryan, you are a gem my friend. Whilst I hadn't intentionally separated some connectors when I moved the assembly I must have inadvertently separated a connector which I have just discovered and all is now well.
I owe an awful lot of you guys a pint each for the help you give. Thank you
Bryanj:
People are frightened by electrics but if you are methodical its actually easy, long distance diagnosis is not very easy and i find if i give precise instructions on testinga lot of people disapear off on a tangentand i am afraid at this point i tend to give up and go quiet, you are at least listening!!!
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