Topic: 76cb550k electrical issues

[76 cb550]

PO was a strange guy... I've been looking at this for a bit now and I can't figure out how to undo what he's done.  I believe it involves the taillight but I'll wait for a little feedback before I start digging into it further.  Last time I checked all the lights worked.  Maybe my mind blinked and I forgot to check something but I think everything worked. 









Let me know if you need more info

[Gordon]

Looks to me like the fuse clip for the main fuse melted the plastic holder, so someone removed the fuse from the line and taped the wire to itself.  As you've discovered, the bike will work just fine like that, but only until something shorts out and the wiring harness catches on fire because there's no fuse.

[Gordon]

You can replace the fuse block or just add a single 15amp fuse holder.

[TwoTired]

That's pretty sad bike abuse.  Those fuse clips were bright and shiny when new.  The oxidation on them is resistive and causes heat that, at first, melts the fuse.  They probably put ever larger fuses, in there until the heat stopped melting the fuse.  But, instead then melted the plastic. 

Your going to need a new fuse block as now, only your lighting is fused.  I'd guess they wired the main direct, eliminating and fuse for the main.  Now, if an over current occurs, it will destroy wiring.  Looks like they buggered both the fuse holder harness and the bike wire harness connections.

Were it mine, I'd restore the wires to the harness connector and replace the fuse block assembly  If you get a used one, be sure to clean and polish the fuse clips bright and shiny.
 
Cheers,

[mark]

Fuse box meltdowns are fairly common on these machines. Some folks eliminate the fuse box entirely. I left mine in there just for looks - in case I pull the sidecover for some other reason.

Stock terminals removed from the plastic connector body, cleaned up a bit, applied shrink tube, plugged in blade fuses. Fully functional, completely reversible if the resto bug bites, improved access as the fuses are now under the seat.


Happy trails.

[76 cb550]

so the 1 blue and 2 white bits are fuses?  Interesting Idea.

I've got the fuse box of a 77 waiting to be put on.  I'm planning on switching them out soon.  Along with the wires that go from the fuse box to the first plastic connector.  Then I'll disconnect the loose wire that he spliced and set everything back to right.  I think I can handle it now.  If I have a ton of trouble getting it back the way it should be I might try those blade fuses. 

I have a question.  The bike shifts wonderfully but the screws on the transmission show signs that someone has been in there before.  Considering my PO's quality workmanship up until this point should I consider going in there and poking around just to make sure everything is as it should be.  The transmission scares me a bit.  It was one of the things I was hoping to avoid during this.

[cafe750]

If you're talking about the screws that are in the sprocket cover, that are on the outside of the bike, then the PO probably just had it off to change the front sprocket. You cant actually get to the guts of the transmission through that cover....hope that helps a little. 

[Gordon]

You cant actually get to the guts of the transmission through that cover....hope that helps a little. 

Yeah, you have to completely dismantle the engine and split the cases to work on the transmission.

[TwoTired]

I have a question.  The bike shifts wonderfully but the screws on the transmission show signs that someone has been in there before.  Considering my PO's quality workmanship up until this point should I consider going in there and poking around just to make sure everything is as it should be.  The transmission scares me a bit.  It was one of the things I was hoping to avoid during this.

I expect you are talking about the left side engine cover/sprocket cover.  You do not gain access to the transmission with this cover removed.  However, the oil pump, oil sending unit, front sprocket, and shifter seal are accessible there.  Given the other foibles found on your bike, and the signs you've mentioned, I think I agree with you the a look inside is warranted.  Particularly so, if there are signs of oil weep from this area.

I suspect you'll need an impact driver to remove the cover screws.  Note what length goes in which hole.  The shift lever bolt must be removed before the shift lever slides off.  Mark its position on the splined shaft so you can put it back on in the same place. Also, the left foot peg gets removed.  Then the cover.  Have a look inside and clean things up.  Look for scars and acts of barbarism.   Check for front sprocket wear, too.
Cheers,

[Gordon]

Look for scars and acts of barbarism. 

For some reason that sentence makes me laugh...

Sounds like advice one might give to someone going on a first date.

[HondaMan]

Hmmm...this just keeps reinforcing an idea I'm entertaining (for the riders who are not "resto oriented", but "resto-mod interested")...we've all seen those "chopper conversion" devices that are sort of generic replacements, often very "clean" assemblies, that replace the worn connectors and parts seen here.

If I were to create a nice, clean, SMALL assembly that includes 3 fuse holders, solid-state flasher, heatsinked silicon rectifier, voltage regulator/limiter, and places for 2 optional cube relays, would SOHCers be interested? It would fit a lot more than SOHC bikes, but be engineered specifically for them...it would be overbuilt the way my ignitions are overbuilt, for VERY long life.

[Gordon]

If I were to create a nice, clean, SMALL assembly that includes 3 fuse holders, solid-state flasher, heatsinked silicon rectifier, voltage regulator/limiter, and places for 2 optional cube relays, would SOHCers be interested?

What do you think something like that might cost?  I realize you can't give an exact figure right now, but a ballpark?

[TwoTired]

Look for scars and acts of barbarism. 

For some reason that sentence makes me laugh...

I suspect it makes you laugh because you, too, have worked on machines with previous owners.  What with the trashed screw heads, over torqued bolts, duct tape, bailing wire, and bent accutrements, I refer to most previous owners as "Connan, Blogg, or Crag". Or, almost any name that equates to "He that has little use of neurons".

Cheers,

[76 cb550]

Look for scars and acts of barbarism. 

For some reason that sentence makes me laugh...

I suspect it makes you laugh because you, too, have worked on machines with previous owners.  What with the trashed screw heads, over torqued bolts, duct tape, bailing wire, and bent accutrements, I refer to most previous owners as "Connan, Blogg, or Crag". Or, almost any name that equates to "He that has little use of neurons".

Cheers,

Wow twotired.  It sounds like you've become intimate with my bike.  I have all of those things in abundance on my bike.  Not sure if I mentioned this in the other thread but the PO was very fond of using duct tape as an insulator(electrical tape).  I think that might be the most telling thing I've found so far. 

If I were to create a nice, clean, SMALL assembly that includes 3 fuse holders, solid-state flasher, heatsinked silicon rectifier, voltage regulator/limiter, and places for 2 optional cube relays, would SOHCers be interested?

What do you think something like that might cost?  I realize you can't give an exact figure right now, but a ballpark?

I second that question.

Look for scars and acts of barbarism. 

For some reason that sentence makes me laugh...

Sounds like advice one might give to someone going on a first date.

For a new rider (aka ME) it is A LOT like giving advice to someone before a first date.  And I appreciate all the advice I've gotten thus far. 

[HondaMan]

Right now, I'd estimate around $100, but probably less. I'll have to look around at voltage regulators that could work cheaply, like maybe Ford units, that will integrate easily. The fuseholders would likely be the common automotive bladed type, since the contacts don't lose their temper or surface qualities as readily as the original Honda ones did. It should be small enough to mount across the existing frame supports under the side cover(s), with the relays possibly on the inside of the plate. The plate itself would be the heatsink for the rectifier(s). I've been thinking about this thing for a while.

Two Tired hit the source of the fuse failure problem right on the button: these clips get corroded and hot, then lose their grip and conductivity, causing heating of the fuse ends. The fuse ends are solder, which then crystallizes (or melts outright), making more heat and destroying the fuse element itself, at loads as low as 7 or 8 amps. Going from a failed 15 amp fuse to a 20 amp solves it for a while, but this just bandaids the real problem. Eventually, the 20 amp fuse may get tested by a short somewhere, which then damages the splices in the black "backbone" circuits in the harness, and overall failure looms...

[76 cb550]

Well I cleaned up the connections and spliced a length of wire to the broken wire.  I also put the fuse box in.  Had to hack it up a little to make it fit.  I had two extra slots for fuses and I had to remove one of those slots with a set of diagonal pliers to get the side cover to fit properly.  Haven't tested it yet.  The fuses for the 77 are WAY bigger than the 76.  the 77 uses 32's and the 76 uses something like 7 15 10.  The fuses fit but it isn't a really good fit.  Do you guys think it'll still work?  If it was the other way around and I was going from big fuse box to small I wouldn't think of trying it out but smaller to bigger with a decent fit?

[TwoTired]

The 77-78 cb550 models came with 7, 7, and 15 A fuses.  Prior years used 5,7, 15A fuses.  either choice is appropriate for your bike.  All the models were supplied with 1 inch length fuses.  While 1 1/4 length fuses are more readily available at auto stores, they are incorrect for the stock fuse holders, and don't make full contact with the fuse clips.  The reduced contact can also lead to fuse clip heating, as it restricts current flow to a smaller area.

Don't confuse a 32 volt rating on the fuse with an amperage rating, which should also be marked on the end cap.

Cheers,

[76 cb550]

it's not just the fuses that are larger.  The slots for the fuses are much bigger too.  Edit:bigger=further apart  (i'll take pics if you want them)

[TwoTired]

You sure it's from a 77 CB550?  I'd like to see a pic.  Your old and replacement side by side?

Cheers,

[76 cb550]

can do...brb

[76 cb550]

I have a mixture of fuses in each box to help compare sizes.  the smaller fuses go with the old box that I'm holding the larger go with the new box on the bike

[TwoTired]

First I have something of an apology to offer.  Previously, I said all models used the same length 1 inch fuse.  After seeing your pictures, I got off my butt and took a closer look and measured my 77 fuse holder.  They are still stuffed with factory supplied 30mm (1.183") fuses, not the 25.4mm (1") fuses used in earlier fuse holders.  So, you would, indeed, be better off with 1.25" fuses than the shorter 1" in the newer fuse holder.  Sorry about misleading you earlier.

The fuse clips are supposed to "float" a little bit in the black plastic holder, so that the clip sides will self align with the fuse end caps for maximum contact.  If the fuse clip gets hot enough to melt the black plastic, the clip "float" ability is usually lost.

In my opinion, neither of those fuse holders look like they'll be reliable in the long term, and is a road headache waiting to happen.  If you decide to use them anyway, be sure to polish the clip contact surfaces AND the fuse end caps for bright, shiny, mated contact.
Also check the clip retention ability.  If you can pull out fuses with your bare fingers, the clips aren't grabbing like they need to.  You should need a tool to pry them out, unless you push them lengthwise out of the clip grasp.

Did you rewire the terminals on the back of the 5 position block?  The end fuse clips aren't normally wired at all, as they are spare fuse holder positions.

Cheers,

[76 cb550]

no need to apologize.  I really shouldn't have taken your word for it (no offense intended).  It was a good lesson for me.

I'll consider getting a new fuse box.  I'll be using this one for a while though$$$

I did rewire the terminal.  I wired it the same way that it was wired before.  I assume your confusion comes from the fact that the fuse box is upside down.  I could only get it to fit properly by cutting off the 5th fuse and turning the whole thing upside down.  I cleaned the  fuse connections but I'll go file them next chance I get and make them nice and shiny.

I can remove the fuses with my fingers but it's hard.  I can tighten the connections up a bit without much trouble.