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Cb550f blowing main fuse
Towsejames:
Hi,
I’ve finally got my 550 on the road and riding for the first time with me just in time to catch the last of summer - (since I think 1999). A lot of titivation changing and rebuilding carbs, fork seals, tubes tyres, electronic ignition, servicing and lots of cleaning up.
I am sussing out some teething issues since taking it on short journeys where I live to try and make it reliable. It has broken down on me a few times but nothing a little roadside fix and cleaning up and improving electronic connectors didn’t solve.
However my latest breakdown blew the 15a main fuse losing all electrics to the bike, luckily a spare was there which allowed me to get home - something to note is I rode the bike for about 5-10 mins with the headlights on for the first time when the fuse blew. With this in mind I rode home using only the pilot lamp which seemed to be fine, around 2 mins from my house I switched my headlight back on which lasted the 2 mins home blowing the main fuse again right outside my house. The headlight thing could be a coincidence but they do also seem abit dim even though the bike charges.
Has anyone had the main fuse blow?
My plan is to replace the fuse box for a newer blade type anyway checking for any bad connections along the way.
Thanks for any help
Sent from my iPhone using Tapatalk
Towsejames:
Sent from my iPhone using Tapatalk
K2-K6:
You haven't got any led bulbs in replacement for conventional items installed have you ?
Just a thought, as if there's failure on some of these they can give a resisitive short to ground, which then puts some demand in capacity on main fuse.
In other words, the headlight then looks like culprit, but it's the diminished capacity giving less headroom that causes failure.
Just a reality check, can be ignored if not present.
Otis:
--- Quote from: Towsejames on August 10, 2026, 10:15:26 AM ---Hi,
I’ve finally got my 550 on the road and riding for the first time with me just in time to catch the last of summer - (since I think 1999). A lot of titivation changing and rebuilding carbs, fork seals, tubes tyres, electronic ignition, servicing and lots of cleaning up.
I am sussing out some teething issues since taking it on short journeys where I live to try and make it reliable. It has broken down on me a few times but nothing a little roadside fix and cleaning up and improving electronic connectors didn’t solve.
However my latest breakdown blew the 15a main fuse losing all electrics to the bike, luckily a spare was there which allowed me to get home - something to note is I rode the bike for about 5-10 mins with the headlights on for the first time when the fuse blew. With this in mind I rode home using only the pilot lamp which seemed to be fine, around 2 mins from my house I switched my headlight back on which lasted the 2 mins home blowing the main fuse again right outside my house. The headlight thing could be a coincidence but they do also seem abit dim even though the bike charges.
Has anyone had the main fuse blow?
My plan is to replace the fuse box for a newer blade type anyway checking for any bad connections along the way.
Thanks for any help
Sent from my iPhone using Tapatalk
--- End quote ---
Hi James,
I had exactly the same thing a few months back with my 350 Four and had to call the AA. The chap replaced the main fuse and suggested following me home in case it went again, well 3 miles up the road it did and he transported me home.
A week before I had replaced the bulbs in the dashboard, tacho and speedo so thought this would be the best place to start. Inside the headlight the wires are a right mess but I methodically checked each circuit and found a bad connection. Repaired the bad one and double checked the others. Put in a new fuse and all has been perfect ever since. I have to say I was somewhat surprised at how disabled the bike was with a dodgy main fuse.
Happy hunting and hope you find it uickly because it is very annoying.
Cheers
deltarider:
--- Quote from: Towsejames on August 10, 2026, 10:15:26 AM ---Has anyone had the main fuse blow?
--- End quote ---
O, yes, over 46 years a couple of times, but not any more since I've made it a habit at the start of the season to clean the ends of the main fuse and the clips that are holding it. If these contacts are not clean or are even slightly oxidised, under circumstances the fuse will blow. Always have a spare with you but do not position it before you have carefully inspected cq cleaned its ends and the clips. The 5A (taillight) and the 7A (headlamp) are still the ones the bike got on 1976 at the assembly line.
In spite of a 60/55 Watts H4, 3 ohm coils in combination with a transistorized ignition, 15A has always served me.
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