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Cb550f blowing main fuse

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Oddjob:
It's a bad bodge then, you risk a fire doing that.

Otis:

--- Quote from: taysidedragon on August 17, 2026, 04:40:23 PM ---
--- Quote from: Otis on August 17, 2026, 01:27:10 PM ---
--- Quote from: Oddjob on August 16, 2026, 06:38:56 PM ---30amp is way too high. 15 is more like it.

--- End quote ---

Thank you for confirming as I only replaced the first one with what was already in there. Even the Haynes manual doesn't appear to give guidance on fuse ratings but that doesn't surprise me. In the last 50 years I have never found a Haynes Manual to be useful: it only gets you into deeper trouble because it gives the impression it is thorough but they are pretty much all useless.

--- End quote ---

Maybe that was a bodge by the previous owner because it was blowing 15A fuses?

--- End quote ---

That sounds very likely because there have been a couple of iffy things that I discovered.

Bryanj:
I think you need to start from scratch with an ampmeter that can handle 30ish amps put in circuit DO NOT USE THE STARTER!!!!

Dissconnect everything then start carefully reconnecting and wiggling(technical term!) all the wiring and connectors to see if you can get a high current draw.

Primary suspects from years of problems are :-

Idiot light bulb holders
Wiring under seat
Indicator wires through stems
Rats nest in headlamp
Wires through the bars

Otis:
That's useful information, thank you.

OK, so I have done as you suggest and replaced the fuse again and turned everything off. The battery is reading 13.3V.

Ignition on - no problem
Headlight on both dip and full - no problem
Horn - no problem
LHS indicators - performing as expected
RHS indicator front bulb just stays on and doesn't wink and the RHS rear bulb does not light up at all. I swapped bulbs and it isn't the bulb so first area of suspicion!
Front brake lever operates the stop light with no problem but footbrake does not operate the brake light so second area of suspicion!
Kick started the bike and she runs as expected but the two identified areas of suspicion remain the same.
During these checks nothing appeared to blow the fuse again which is perhaps disappointing.

If any of the above suggests anything to anyone and can possibly narrow down the areas to attend to next it would be really appreciated.
 

Bryanj:
Both those items have wiring under seat.
Rear brake light switch first connectors are in the rubber boot where yellow and blue wires from points join into loom, bulb should light if black and green/yellow joined, if yes new switch if not wiring.
Indicator will be either light blue or orange and connect in big rubber boot under seat near to seat support accross frame, first use a seperat earth wire from ind body to batt neg, wouldnt be first time a slightly loose mounting stopped on working!

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