Topic: 1975 cb550 electrical issue

[Yert315]

Hey guys, I hope you can point me in the right direction. I've been dealing with a 1975 cb550 that had been sitting for over a year (apparently running before that). I'm not an electrical genius so take it easy on me please!

I am getting about 12 volts at the battery. The voltage drops to 10.5 after the main fuse. In the bundle of wires under the left side of the tank I'll get as little as .05 volts on a switched
hot wire.

The headlight comes on, but is dim. The starter does not kick over unless I jump the solenoid. Turn signals and gauges light up.
My uneducated mind wants to think there is an open circuit somewhere not completing a ground? I've gone through the wiring diagrams and everything looks to be where it should.

Any guidance is appreciated!

-Trey

[eastyork1977]

I'd clean and reconnect all the connections and get a new Rectifier regulator. You could have a weak ground or multiple gremlins in the harness. Redo all of them and see if that harness is still good. Main battery ground could use a good shine up too. If you want to know what it is that's causing the issues, do it step by step including all lights, components and controls. Its time and or money either way.

[calj737]

If you are seeing a drop from 12v (what is it actually, measured with a meter at the battery?) to 10.5v passing thru the fuse, then the most likely culprit is the fuse block itself. The clips that hold the fuse corrode on both sides (facing outward, and on the backside) after time. To correct this you can remove the fuse block and carefully clean both sides until shiny bright, or replace the block with a modern styled ATC fuse block. Hondaman (Mark) makes a plug and play replacement unit that you can find a link to in the Services Offered forum.

Full maintenance of all connections, grounds and the terminals is in order, but the fuse resistance is a major priority. You should also verify that the battery itself is good. If you see the voltage drop with the key active (10.5v at the battery) then it's a strong indicator your battery is toast.

[Yert315]

Thanks guys.
I am testing the voltage with a voltmeter. 12.3ish volts when off. Same when the key is turned on. Voltage does not change when I hit the starter button either. (Holds steady).
I will have another look at the grounds. I don't see any visible corrosion on any of the connections, though I will clean them all just to be safe.

I bypassed the main fuse all together by connecting the wires directly to one another (temporary - for testing purposes). Still showing a voltage drop.

[calj737]

If you bypassed the fuse, where then are you reading the voltage with the key OFF to get 10.5v?

[Duanob]

Yep. of cleaning of terminals and such. As Calj says the fuse blocks are prone to over heating and melting so take it out and inspect it and all the connection blocks. Also you can take the starter solenoid apart and clean it as well. They tend to get corrosion on metal connections from sitting especially in a damp enviornment. Get your self a multi-tester and a wiring diagram. Here is a good source for electrical diagnostics and supplies:

http://www.oregonmotorcycleparts.com/FAQ.html

[Yert315]

sorry, my story is misleading.
key is ON when checking voltage.

I originally checked voltage at the Battery with key on, off, and while hitting starter button. This was to rule out battery.

[calj737]

So after bypassing the fuse, where are you getting 10v measured? And is it with or without the key ON?

[Mantree]

After 41 years your wording might be corroded causing high resistance I ended up rewording my invite 74 because of wires that were so bad I was only getting 6v at the coils

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[DaveBarbier]

After 41 years your wording might be corroded causing high resistance I ended up rewording my invite 74 because of wires that were so bad I was only getting 6v at the coils

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Don't think grammar is the issue here

[Mantree]

After 41 years your wording might be corroded causing high resistance I ended up rewording my invite 74 because of wires that were so bad I was only getting 6v at the coils

Sent from my ME302KL using Tapatalk

Don't think grammar is the issue here

Autocorrect makes me look like a idiot alot

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