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Author Topic: It died on me. Need advice.  (Read 2170 times)

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Offline tofan

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It died on me. Need advice.
« on: July 27, 2018, 10:58:11 AM »
I have a 1976 CB550.

Bike has been running like a champ until...I was driving home the other day and the bike started choking, backfiring and eventually died on me. There's no electrical power running through the bike anymore. Turning on the ignition gets nothing.
The first thing I did was charge the batter overnight. Still nothing. At first glance the wiring seems fine, nothing obvious. The three fuses are good.

Electrical problems are my achilles heel. Any advice on how to go about troubleshooting such a problem?

Everything is stock. No modifications. The battery is about 3-4 months old and the coils are about a year old.
« Last Edit: July 27, 2018, 11:47:41 AM by tofan »
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1976 CB550K
1976 CB750F
1978 CB750F

Offline Bankerdanny

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Re: It died on me. Need advice.
« Reply #1 on: July 27, 2018, 11:40:00 AM »
It can look daunting, but the electrical diagram becomes easier to understand the more you look at it.

If you have access to a printer with 11x17 size paper I highly recommend finding a copy of the schematic with a high enough resolution to allow for printing on that scale. More than just making it easier to read for middle aged eyes like mine, it makes it easier to follow the path of the wiring.

Our bikes are pretty basic with no computers and only a couple of stock relays. Be systematic and you can figure it out. Start at the battery, follow the power to the switch, then out of the switch to the right side control and the fuse block. You can do it.

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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline 2wheels

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Re: It died on me. Need advice.
« Reply #2 on: July 27, 2018, 11:43:25 AM »
Check the fuse.
Clean the battery terminals.
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1970 CB750 K0 (I can't believe I tossed my duck tail seat in the trash 30 years ago)

Offline cooldrum

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Re: It died on me. Need advice.
« Reply #3 on: July 27, 2018, 12:59:52 PM »
The fuses may look ok visually, wouldn't hurt to replace them and clean the contacts. Keep us posted.
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Offline seanbarney41

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Re: It died on me. Need advice.
« Reply #4 on: July 27, 2018, 01:10:13 PM »
If the fuses and fuse block are good, I would guess the key switch has failed.  Check out a wiring diagram and you will see how easy it is to hotwire your bike for testing.
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If it works good, it looks good...

Offline Stev-o

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Re: It died on me. Need advice.
« Reply #5 on: July 27, 2018, 02:09:11 PM »
Quote from: cooldrum on July 27, 2018, 12:59:52 PM
The fuses may look ok visually...

...but check them with an ohmmeter to confirm they are good.

I'm with Sean...betting a dollar its the ignition switch if the fuses are indeed good.

Check all connections while you are at it.  It is something basic...
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'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Stev-o

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Re: It died on me. Need advice.
« Reply #6 on: July 27, 2018, 02:57:10 PM »
Quote from: calj737 on July 27, 2018, 02:31:22 PM
Quote from: Stev-o on July 27, 2018, 02:09:11 PM
Quote from: cooldrum on July 27, 2018, 12:59:52 PM
The fuses may look ok visually...

...but check them with an ohmmeter to confirm they are good.

I'm with Sean...betting a dollar its the ignition switch if the fuses are indeed good.

Check all connections while you are at it.  It is something basic...
His initial description was it died a “sputtering and coughing” death, then nothing. This is symptomatic of a depleted battery unable to fire the coils.

Good point Cal.    Tofan...got gas?!
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'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Stev-o

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Re: It died on me. Need advice.
« Reply #7 on: July 27, 2018, 06:10:00 PM »
Quote from: calj737 on July 27, 2018, 03:05:31 PM
Quote from: Stev-o on July 27, 2018, 02:57:10 PM
Quote from: calj737 on July 27, 2018, 02:31:22 PM
Quote from: Stev-o on July 27, 2018, 02:09:11 PM
Quote from: cooldrum on July 27, 2018, 12:59:52 PM
The fuses may look ok visually...

...but check them with an ohmmeter to confirm they are good.

I'm with Sean...betting a dollar its the ignition switch if the fuses are indeed good.

Check all connections while you are at it.  It is something basic...
His initial description was it died a “sputtering and coughing” death, then nothing. This is symptomatic of a depleted battery unable to fire the coils.

Good point Cal.    Tofan...got gas?!
He said “nothing in terms of power/electrical”. Not a fuel issue  ;)

Covering all the bases!
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'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline tofan

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Re: It died on me. Need advice.
« Reply #8 on: July 27, 2018, 11:06:59 PM »
Thanks all for your input. I will start looking into it this weekend and update you all. Baby steps.
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1976 CB550K
1976 CB750F
1978 CB750F

Offline Marks78

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Re: It died on me. Need advice.
« Reply #9 on: July 28, 2018, 09:22:02 AM »
Download the "Electrical fault finding chart" from this website. It has a great bit of information.

http://www.electrosport.com/technical-resources/diagnosis-center/fault-finding-guide

Finding electrical problems is a true test of patience but take it slow and be very methodical about it and you can figure it out!  Best of luck!
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Current Stable:
1978 CB750K
1982 XT200J
1982 XJ1100 Maxim
1985 V30 Magna
1998 VT1100 Spirit
2006 GoldWing

Offline tofan

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Re: It died on me. Need advice.
« Reply #10 on: July 28, 2018, 01:34:11 PM »
Turns out the power (red) wire in the ignition switch assembly had snapped off at the solder point. I managed to hotwire the bike just fine.

In the process I tested the primary resistance of the coils and they're reading at about 5.1 ohms. Is that normal? I thought it was supposed to be around 3 ohms.
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1976 CB550K
1976 CB750F
1978 CB750F

Offline evinrude7

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Re: It died on me. Need advice.
« Reply #11 on: July 28, 2018, 01:56:12 PM »
Quote from: tofan on July 28, 2018, 01:34:11 PM
Turns out the power (red) wire in the ignition switch assembly had snapped off at the solder point. I managed to hotwire the bike just fine.

In the process I tested the primary resistance of the coils and they're reading at about 5.1 ohms. Is that normal? I thought it was supposed to be around 3 ohms.

stock coils should read about 5 ohms.

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cb750 k6 - ugly

Offline Marks78

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Re: It died on me. Need advice.
« Reply #12 on: July 28, 2018, 02:13:11 PM »
Glad you got it figured out!
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Current Stable:
1978 CB750K
1982 XT200J
1982 XJ1100 Maxim
1985 V30 Magna
1998 VT1100 Spirit
2006 GoldWing
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