Topic: 75 cb550 Main Ground

[c(b)hris]

75 cb550k.
The bike is kick only.  The solenoid is removed.
The big black ground wire that goes to the starter, can this be removed or does it need to be connected to the battery negative cable still?

[HondaMan]

There needs to be 2 grounds in the system.
A large one must go between the battery (-) post and the engine and frame, together. This provides the base electrical ground system. This one must be able to carry the full power of the alternator and any discharge the battery can supply: a typical 12 AH battery can source over 50 amps for long enough to burn down a wire smaller than 8 AWG, hence to big size of the ground wire. That hot wire, with some grease on it, can also burn down the bike. 

A smaller one is used for the coil and lights return to the frame. This is the Green wire in the harness. It can be connected to the frame at either the front, where the coil brackets ground to the frame, or at the rear, under the seat, directly into the frame. This one should me about 18 AWG at the smallest.

[c(b)hris]

awesome, thank you very much

[bryanj]

Just for info there is NO big black ground wire to the starter---the big wire to the starter is a power wire, The ground wire goes to the RH rear engine mount plate and there must not be any paint or powdwer coat where it connects

[HondaMan]

Just for info there is NO big black ground wire to the starter---the big wire to the starter is a power wire, The ground wire goes to the RH rear engine mount plate and there must not be any paint or powdwer coat where it connects

Roger that!
I once got a 750 delivered in my backyard, via pickup truck, that was freshly powder coated, looked great! But, didn't run after the first startup. The entire main body of the wiring harness was a melted mess. Turns out the ground lug at the frame was pinched between the powder-coated frame and freshly (and thickly) painted engine, and the engine hangar bolt was rusty its whole length, acted like it, too, was insulated from the inside contact at the frame and engine. When the owner had cranked away with the electric start, hooked up to a car battery for assistance after the rebuild, the starter was grounding via the Black wire circuit, up to the front coil mounts.

In those days, PartsNmore wasn't yet selling harnesses, so I got to rebuild one by hand.

[c(b)hris]

so the thick black wire that goes to the starter on the cb550 is actually positive?
I guess that makes perfect sense, and I feel pretty dumb for having that connected to ground.. geez.

another question, without the solenoid, the main positive wire from the battery, can it be a smaller gauge wire?  can it be say 14 gauge since the starter motor never has to draw anything from it?

[mono]

No, it's like HM said-- the thick black wire is your negative frame ground, needs bare metal contact.  The thick Ted wrote goes from the battery positive to the starter solenoid.  I'll go take you a picture in a minute.

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[mono]

You don't want to reduce the wire sizes probably.  They're thicker for a reason (something to do with science, don't ask me)...

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[mono]

Eh... it's too cramped for a good pic.   Check out a wiring diagram, all will be clear. 

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[HondaMan]

so the thick black wire that goes to the starter on the cb550 is actually positive?
I guess that makes perfect sense, and I feel pretty dumb for having that connected to ground.. geez.

another question, without the solenoid, the main positive wire from the battery, can it be a smaller gauge wire?  can it be say 14 gauge since the starter motor never has to draw anything from it?

The Red wire circuit between the Battery (+) and the rectifier (+) terminal needs to be either large, or made of a fireproof jacket like MTW or SXF jacketing, if you care to follow 'official' rules today. If you were to "build" a bike for someone, this has become [yet another overreach of] a fed regulation, so the bike can't catch on fire from wiring deficiencies. I make replacement fuseblocks for these bikes (multi-fuse versions after 1973) and had to go through all that [stuff] just to make them 'safe for mankind'.

If you make the Red wire 14-16 AWG in short length (less than 12" total to the rectifier), even with PVC insulation like you find at Auto Zoo (called "Automotive primary wire"), it should never actually get hot enough to be a problem. The main reason to use good wire jackets, though, is the weather and the alkaline soaps at the quarter carwash: both can make PVC brittle, and cold can make Teflon (THHN jackets) crack and split. So, try to find some SXL, GXL, or TXL wire, if you want best results. I think you can get small quantities of it from Del City and places like that.

The bike's loads beyond the rectifier are typically 11 amps or less, so a size 18 AWG will carry those loads with no issues, if it's not PVC.

[dave500]

the starters black wire only becomes positive when you hit the starter button,and you have a solenoid or starter relay in place,and its all hooked up correctly.