SOHC.co.uk Forums > CB500/550
Electric problem
Lobo:
Hi again Bomber,
Regarding the (bad looking) main cables to your battery (ie Picture #2) and your comment, "I think this is to blame for the bike's poor charging & general misbehaving".....
If the electric start is cranking the engine then these lousy looking cables are still capable of carrying 120A or so.... Ie way above any max charging current which, for the CB750 is approx 13A.
In other words, despite their condition they are unlikely to be blamed for charging issues. (but still need replacing)
The red / white wire from the rectifier is basically the charge coming from your alternator, and likely terminates at one main lug of the starter solenoid. From here (the same lug) the charging current continues (via the heavy duty red cable) to the positive battery connector.
If you are having charging problems my guess is its in this red / white lead given your photo of burning through the rubber insulator - ie the connector area is corroded to the point it can't efficiently carry the current needed & so begins to overheat....
I agree that if able to fix yourself; well it's always better for obvious reasons, but as suggested don't 'bodge' as whilst some roadside repairs are easy, electrical gremlins are not!
You mention your 60W headlamp was draining the battery.... on a healthy CB550 I'd be surprised given the alternator's capability... and this too indicates a charging problem. (let's say you're running night load might be 60W head, + 5W tail, + 20W brake, + 40W indicators, + 20W alternator field coils etc = 145W, divide by 12V ... to give a current draw of approx 12A..... right up there agreed, but you generally don't ride around with the brake light on / indicators flashing. (ie 'normal night load of (60+5+20) / 12 = 7Amps or so.... easily within the alternator output.
Yesterday I said I knew of no short cut to cleaning connectors etc (still true!) - but a useful tool is a small Dremel with the small various wire wheel attachments they offer.
Anyways, good luck, a basic 400F diagram which may not be accurate, but will be approximate until you can lay your hands on a quality one pertinent to the 500/550F
(the rectifier is bottom right, the Alternator the blue circle left of this)
Simon
bomber:
Thanks lobo for explanation, much appreciated.
I had a closer look at the connections and to my surprise they are riveted to rectifier?!
I'm confident that there is just enough red/white cable to fix it but will have to loose black sleeve.
I have ordered cables as you suggested, went for 170 might be over kill but it will definitely let juices flow easier then now :)
I have been looking for a while at the dremel you mentioned, I'm afraid for now elbow grease will have to do ;D
I have another question, what are cable specification which is used in loom? I have seen a post while back which I cant find any longer, can some one point me in right direction?
Many thanks
bomber:
Found that post!
The recommendation was 32/0.20mm, 1mm2, 16.5amp.
Thanks to the-chauffeur and LesterPiglet!
Lobo:
Aha, great!
Ok, just to further help (?); your bike's main fuses are rated @ 15A (?).... and so basically chose a spec of wiring that is greater than this...
http://www.autoelectricsupplies.co.uk/category/10
If you look here, you'll be given an option of 'Standard' or 'Thin walled' cabling, ... read the intro blurb. I think (somebody confirm?) that the thin walled, whilst lighter & more robust, is 'stiffer' and a bit more of a pain to bend / use... but it's the industry standard & so obviously ok.
For 'end of looms' ... eg a block connector to an indicator bulb, or the switched feed to the horn (etc) you can go for a lower / lighter spec of wire using the formula in my previous posting... ie Watts / Volts. .... eg a single indicator @ 21W / 12V would imply only 2A spec necessary for the stalk wiring. But why make life complicated... my Honda is the same gauge wire throughout its loom BARRING that red / white charge & main feed to the ignition... I seem to recall.
Yup, now remember the 'riveted' connections to the rectifier (I recon'd my 400 loom last year), I guess Honda want to guarantee a good & vibration proof connection. My guess is you have this at the spade... but the actual copper strands into the spade are badly corroded. If this is the case you'll have your work cut out paring it back to good / fresh copper.... and again, good luck!
Simon
Lobo:
... just something else Bomber... You said above
"Another thing is I have strange cable I suppose earth going from negative terminal all the way to ignition coil, it looks like a recent upgrade..."
.... & gotta say, this sounds a bit odd. Are you sure it actually connects to the coils.... or as Brian says, "there ought to be a cable in the loom going to the coil BRACKETS" (this wire will be likely Green, and earthing the coil units to the frame versus directly connecting to the coils wires.
Point is, the L & R coils, are earthed through (their Yellow & Blue wires) and the contact breakers. If a permanent earth was fed to these wires you'd never achieve a spark, and the engine (obviously) wouldn't run.
The other wires (blacks) are 'live' in, and via a common feed from the ignition switch & through the kill (emergency) switch. (which is why you shouldn't leave the kill switch on with ignition (engine off) as current will run through the coil and complete its circuit to earth if a contact breaker is closed... ie you may burn out that coil)
Bottom line, if your coils input wires are somehow directly earthed from the battery then I'm flummoxed!
In the neat sketch below (alas not mine) the tail & head lamps are obviously missing their earth connections.... I guess the intention being they're mounted to the frame. Starter motor & Points ditto. I reckon the 'Acc' position is 'Accessories'?
Simon
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