Author Topic: 76/550.starting problems.magnetic switch,high beam mystery,or starter motor?  (Read 2596 times)

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jr sheetz

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hello all.
so i bought my 76 cb550 three days ago from it's original owner who told me that he was just beginning to have problems with the magnetic switch -it was about to crap out. he was instructed to tap it with a hammer to get the oil/neu lights to come on. this seemed to work fine for him. i was riding it home when it stalled in traffic. i got it started again but then turned the high beam on while fiddling, and it stalled again (the high beam was on the first time as well). no power, no lights, no juice...replaced the magnetic switch with a good used one lastnight and the lights came up, but wouldn't start. so i've charged the battery and got some advice as to what the next step might be. i was told that it could be the starter motor. -and to bridge the poles on the mag. switch to see if it would start. is this okay? or will i create more problems within the system? anyone have experience with this??
thanks,
jr

Offline Kevin D

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jr, do you have a wiring diagram for your new bike? It might be in the owners manual or if you prowl around here you might find one. Are you any good with a multimeter? Open the headlight and check the connections there - they are all color coded and should all be clean and snug. It sounds to me like you might have a problem with your handlebar switch - and the connections are made behind the headlight. I don't have any particular knowledge of the 550, but if you get the meter and the drawing you should be able to track your intermittent.
71 CB750 K1
104,000 miles
Original Owner
———past———
70 SL100/125/150
70 Candy BlueGreen CB 750 K0
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Former Honda parts kid/counter kid/do all
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Offline grumburg

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Had the same problem with my 550. When I bought it, the wiring was a mess. (yellow wire nuts and duct tape). Start by removing the headlight. Do not scream, not as bad as it looks (Ok,it is)  There will be an H shaped connector with 4 black wires connected in it. These are the grounds for the kill switch, headlight switch, turn signal buzzer, and oil pressure and neutral light. Make sure all are tight and no insulation showing. They can short against each other or against the headlight when you push it back in. If these are ok, check the black and white wire that runs to the coil, this is the hot wire for the kill switch. Check for breaks or splices. If you have a 12 volt tester ($5), check for power. Switch the kill switch on and off and see if the light switches on and off quickly. If not, and all other things check out, the kill switch is bad. Also, the black and white wiring diagrams are better that the color ones. 
Fonda Honda

Offline TwoTired

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On US models with stock wiring, the black wires are 12v switched from the ignition switch.  Gounds are all green wires.
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline Bodi

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The best thing to do is get a wiring diagram, the Clymer/Haynes ones are worse than useless because they leave important things out. Example - the headlight circuit does not show that the power goes through the starter button; you could look for hours in total confusion trying to understand why you have no headlight power if you believe the diagram is complete. The Honda shop manual or owners booklet wiring diagram is complete - every wire and connector is shown - but it's a bit hard to understand until you get used to it.
A good start is to remove the tank and headlight, the side covers, and the left engine cover. This should expose all the main wiring connections.
The bullet connectors are pretty nice, they're small and carry the current involved easily when clean and new. The sex is useful too, power is always on a female connector and the load or return is always on a male - the male can easily contact metal and that would mean at least a blown fuse if it was a power wire.
But... after 20 or 30 years the bullets are no longer clean or new. Once corroded and loose they get hot, and can melt the plastic parts. That's why you find the twist-on yellow things, the bullet self destructed and new ones are basically impossible to find - especially multi-tap females - and the yellow twisties do the job.
To prevent meltdown clean the male ends with some steel wool or a scotchbrite pad and the females with a q-tip or a twist of scotchbrite. You can flush the female end out with contact cleaner or brake cleaner (test the brake cleaner to ensure it does not dissolve anything, some formulas do). Smear some dielectric grease around the male end and push it in. If the female is loose and there's no resistance or snap, tighten it GENTLY with pliers.
(do not read the above paragraph aloud in public)
Connect colour-to-colour. The wires can get dirty and all look brownish black but a wipe with varsol or such will bring the colour back.
The muliticircuit connectors on the electrical panel can be cleaned in a similar fashion and the females tightened a bit with needle nose pliers.
Once the wiring harness connections are all good, you can look for problems effectively; many mysterious electrical woes just disappear.

1) the magnetic switch (solenoid) doesn't affect any lights, it just activates the starter motor.
2) The starter motor does not affect the lights, ignition, anything. It is wired directly to the battery through the solenoid switch.
3) The oil and neutral switches are in the engine. Hammering the solenoid to fix a problem suggests trouble in the electrical panel, the bottom plug goes to the engine and has the alternator and oil/neutral switch wires. There's a control box that keeps you from energizing the starter unless the transmission is in neutral or the clutch is pulled in, that may be a problem too; it's on the electrical panel I think. Disconnect and remove the whole panel, check inside for any loose or broken wires or any evidence of overheating.

- The start button shuts off the headlight while starting, this is a common failure point as the switch guts tend to melt when they get corroded and overheat from the (constant) headlight current. Many headlight woes trace back to the starter switch.
- The kill switch is ONLY in the ignition coil circuit and it has no effect on lighting, starter, horn, etc.