Author Topic: 75 CB550. Riding at night and lost headlights brake lights and rear running ligh  (Read 2145 times)

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Offline turin39789

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sitting at a gas station trying to figure this out. bike runs fine fuses all seem okay. limited tools

Offline HondaMan

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Try pulling out the middle fuse, turn it, and reinstall.
If you still have the OEM fuses (SFE type, stamped on the fuse cap on one end) then check for rusty-crusty metal surfaces on the fuse ends. If you swapped them out for modern fuses, then try swapping the bottom fuse into the middle slot instead: the fuse may be damaged. PM for more details when you get home?
See SOHC4shop.com for info about the gadgets I make for these bikes.

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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Link to website: https://sohc4shop.com/  (Note: no longer at www.SOHC4shop.com, moved off WWW. in 2024).

Offline turin39789

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Fuses all appear good. I took apart the switch at the handle but nothing obvious.

Found a flea hotel 4 miles away and got a Good Samaritan to follow me.  while driving they came back on.

when I stop at the hotel they're off when parked. they seem to only stay on when in gear and engine reving. starter has plenty of juice to start the bike
 
« Last Edit: July 18, 2025, 08:24:49 PM by turin39789 »

Offline seanbarney41

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You got an owners manual in the seat still, by any chance?  Owner's manual will have a very good wiring diagram.  First thing I would check is super easy...battery cables tight and clean?  I have had one or the other come loose before and the bike can do very strange things, especially when the bike is stationary.
If it works good, it looks good...

Offline seanbarney41

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Also try fiddling with the key switch and the wires that lead to it.  If you can get to a parts store or hardware a multi meter is gonna really help.  Other things?  Wire and something to cut and strip it. some electrical tape  A 12 volt test lamp would probably get ya sorted if you are savvy and with the other tools you can make one from stuff already on your bike.
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Offline scottly

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The key switch might affect the tail light, but not the headlight or brake light, without also stopping the engine from running. My best WAG (Wild Ass Guess) would be to look for a loose bullet connector in the headlight shell...
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Offline scottly

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Fuses all appear good.
Don't judge a fuse by the way it looks. ;)
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline turin39789

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Fuses all appear good.
Don't judge a fuse by the way it looks. ;)

True. I did swap the ones I had absent the main fuse with no change at rest.

Offline turin39789

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So I managed the remaining 2 hour drive with an abundance of caution at red lights.  At this point I assume it is a weak connection in the wiring that has extra resistance that is overcome when the charging system an engaged.

It was definitely not my night. Once I made the decision to push forward I got a few miles down the road and realized I must not have latched my Bates side bag well enough, and it was the side with a weak safety latch; lost the lid but I think kept all contents. I turned back and made two passes hoping to see it, but the dark was no help.

Somehow when I get on my reserve tank the gas stations always disappear. Never ran out but had some concerns for a bit.

Once I got off the highway and onto back roads, I decided what the night needed was to run into a deer so I planned out that scenario.  Half a mile from my destination, one ran across the road but far enough ahead it was no issue.

Today is a lake day, and then I'll drive back tomorrow in the daytime, and some side of the road checks for my lid on the way.

Offline turin39789

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The key switch might affect the tail light, but not the headlight or brake light, without also stopping the engine from running. My best WAG (Wild Ass Guess) would be to look for a loose bullet connector in the headlight shell...

I did poke around in there to no success.  The harness was replaced a few years ago but some of the headlight bucket connections still look a mess. I checked the headlight connections and a seemed firm.  Turn signals have been out for a bit and may be a separate issue.

When I can make time Il stare at the wiring diagram to pizzle out where these have common connection. Battery is new, neutral/high beam indicator lights are lighting up, starter is strong. All that tells me it's an issue with that circuit.

Offline HondaMan

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While this requires lifting the tank up,,,try unplugging and replugging in the connector of the keyswitch into the main harness. This is near the coils, under the tank. If the blade from the keyswitch on the Brown (+ stripe) wire circuits is loose/dirty/messed up, it will do this (per the wiring diagram) as you described in the beginning of the post.

Since this circuit is also a contact inside the switch itself, and since the Chinese versions of these switches made since 2006 are ALL substandard in their contacts (I have both burned them up in my own bike and found them burned in other's bikes), this circuit could be suspect. When it burned in my 750 (same keyswitch,  BTW) the first symptom was no lights until 3500 RPM, then they tended to flicker. At idle they would go out. Before I got home, though, the bad contact, running hot, melted the Black wire right off the back of the switch and the bike died. In rush-hour traffic.
See SOHC4shop.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book
Link to My CB500/CB550 Book: https://www.lulu.com/search?sortBy=RELEVANCE&page=1&q=my+cb550+book&pageSize=10&adult_audience_rating=00
Link to website: https://sohc4shop.com/  (Note: no longer at www.SOHC4shop.com, moved off WWW. in 2024).

Online bryanj

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Q does this have the "always on" lights where headlight goes off when starter button pressed?

If so that starter button internal contacts could have failed
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline turin39789

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Long update that maybe should have it's own thread.

Finally made it back up to pickup the bike and have another weekend of fun.  Left Sunday morning with the family, had a nice 1 hour drive to the blueberry festival with no issues.

Finally time to go home!  A little low on gas but this time starting off ahead of the family and trying to stay ahead if possible.

Get to the middle of nowhere and have to get onto my reserve.  Bluetooth in my helmet wasn't working perfect to add a stop, but surely I'll find one.

Unfortunately state highway didn't have them marked well, so I passed up at least one before I ultimately coasted to a stop in the middle of nowhere.  My wife of course will never be on board with me riding separately if I call her for gas.  I have a philosophical debate with myself; I check the map and the major town is 11 miles away, before looking in the tank and seeing some precious gasoline.  I slosh it around, tip the left and I'm back on the road!

8 miles later and I'm dead again, and not in a shady spot this time. :( 

One more slosh trick and some kickstarting and I make it the last 2 miles to fill back up.  Woo hoo!

Offline turin39789

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Now I'm a bit further down the road, passing someone who is going just a bit too slow.  As soon as I get past them, I lose some power and my top speed drops by about 10 MPH.

Given the gasoline troubles, I'm mentally thinking there was some sediment in the tank that is gumming up the carb and starving a cylinder. 

Thankfully the situation resolves itself a minute later.  Full power is back!

I'm bad at remembering time, but 10 minutes later and I lose some power again.  Then it's back. Then it's gone.  Then it stays gone.

Thankfully on a highway with a lower speed limit, I stay in the right line while I ponder.  Probably it's gas. Maybe sediment. Maybe I got some bad gas. I try magic tricks. I tap the petcock while driving, it seems to surge back to life for second at a time.  I tap the tank, the carb, very inconsistent results but surely I am on to something.

I finally get to the same gas station where I got stopped on my trip up North, and I'm down to 55 MPH max speed and I need to get this sorted out.

I gas up and go to my trusty diagnostic parking spot from last month. Electric starter isn't happy anymore. Thankfully I just bought a jump box before the last trip.  I break it out, get good lights and full power. 

Weird. Maybe my electrical problems are more than just my headlight issues.  Anyway I'm back on the road inching closer to home.  I'm about 120 miles into my 330 mile trip.

I fill up, poke around but nothing too obvious.
« Last Edit: August 11, 2025, 08:07:54 AM by turin39789 »

Offline turin39789

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At this point my memory is going to blur. I get a short way down the and I start to lose power again. Cautious riding etc, but I'm going to have to stop again, this time on the side of the road. 

Come up with a great stupid idea. I remove the tool tray from under the seat and make room for the little jump pack to rest in there and leave it connected to the battery.

I ride about 5 minutes and begin to question my decision making abilities. Airlines get nervous about batteries, maybe I shouldn't be sitting on one that is being used not for it's intended purpose.

I stop at the next gas station and check it out. Battery is not hot.  I don't want to try and find a 200 mile tow and I don't have anywhere to leave the bike.

I just want to get home. Let's try this out.

I get probably 30 minutes down the road and power slowly starts to go, then comes back etc.  I stop at a gas station.  Set a goal to try and not stop on the side of the road anymore.

Reconnect the jump back connection and I'm off again. 

This stop and go probably happened 3-4 times in total.  Once more on side of road.  Got nervous in Indianapolis with lots of road construction and no breakdown lanes, but low budget bad idea Macguyvering seemed to be holding.


Offline turin39789

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Stopped for gas/re-connect just south of town as I was losing power and was through the construction. I get off my bike to gas up and there is a beeping noise. 

It's coming from inside the house bike! 

I open up the seat and check the battery pack.  Still not warm, but apparently when I was pressing the power check button and seeing full power the whole time it wasn't really.  You press the button, all the % indicators light up and then it shows you the true battery level.

My hack battery is dead.  I have a usb cable but not the wall plug to charge it back up.  I go into 7-11 and contemplate my options and a slurpee.

I buy their finest $30 USB wall wart and find a corner to plug in the battery pack.  My phone is also at this point ready to die.

I let it charge for 20 minutes or so and talk with my wife.  She reminds me it is getting late(7ish) and I had that headlight issue I had not been concentrating on. Debate walking across the street for dinner while my jumppack charges up, but that could take 2 hours with a good USB charger.

More emotional turmoil. Remember I am no longer in the middle of cornfields and find an auto parts store.  None are walkable but I have enough charged the pack enough to get the bike running one more time.

11 minutes later and I am at O'Reilly.  I could have made Autozone or Advance but they were one more block away.  The junior salesperson on duty is a little skeptical but brings the battery tester out and hooks it up.  No result as battery is dead dead. I ask about having them charge it up.  Another customer who just got back from Sturgis gets interested as well and we talk while the test is being performed.  It is noted that the connection to the positive terminal is already loose, not sure if/how that contributes to the woes.

We go inside to borrow an allen key to disconnect the battery.  Senior person on duty is very skeptical.  Their charger doesn't like small connections on batteries.  I ask if we can at least try a half dozen time before we finally get the tool and bring it in.

Magically they must have gotten a new battery charger that has smaller connections.  She gets it connected, and offers me a full charge in ~50 minutes.  I walk across the parking lot for some hot wings and a single beer.

Still worried about the looming darkness, as soon as I finish eating I head back over.  5 minutes to a full charge but I have it pulled early.

Bright indicator lights, fires right up and I am off.




Offline turin39789

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I hit the road determined to go as far as I can in the daylight before I have to turn on the headlights just in case. It's 8pm when I get started and I have 100 miles to go.

I make it about 5 when the bluetooth in my helmet dies.  Thankfully a straight shot from here on out and I know the way, but no tunes or police warnings.

30 miles in and I don't want to be dark anymore.  Headlights are turned on but bike is still running strong.

A little after the halfway point I catch what must have been a monster of a bug that explodes and covers half my visor in gunk.  Then realize it is red liquid, I'm sure it was still just a big old bug but I'm conspiratorial at this point about the forces allayed against me.

Doesn't want to wipe off, so I try riding with the visor open for a bit. At least 2 gnats immediately try to crawl into my eye socket.

I keep going with my squint vision in the full dark.  Still not loving the output on my aftermarket headlight.

I almost make it home in a straight shot, but hit the reserve tank and I'm not playing with running out of gas again.  20 minutes from home I gas up one more time then sprint home and pull in at 10PM.

Offline turin39789

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So the plan from here is to find some time to do the full charging system test that is laid out on the forum to find my problem.

And then I will try to optimize as much as possible.

I picked up some LED indicator bulbs 5 years ago and never installed them. I think I still have some but will try and go LED all the way where I can.

Considering doing the Hondaman transistors just because, as well as the ATC/ATO fuse block. 

I think there are some regulator/rectifier changes that some like and some don't like.  My goal will be to find the culprit and address it and then do whatever is reasonable to make the electrical all around more reliable.

Stock CB550K, but PO had a windjammer at one point.  I've had electrical gremlins before so had the shop throw in a new harness but still doubtful about some of the connections in the headlight bucket.  They had my turn signals working but they have gone back out at this point.

Will post updates as I work through testing.

Offline newday777

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That was quite the ride. Glad you got home.
Where was the blueberry festival?
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline turin39789

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That was quite the ride. Glad you got home.
Where was the blueberry festival?

South Haven MI

Offline seanbarney41

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That was quite the ride. Glad you got home.
Where was the blueberry festival?

South Haven MI
that is a forty minute ride from where I am in Kalamazoo
If it works good, it looks good...

Offline turin39789

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That was quite the ride. Glad you got home.
Where was the blueberry festival?

South Haven MI
that is a forty minute ride from where I am in Kalamazoo

I was even closer then on Saturday on our inland lake day

Offline turin39789

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Quote
Charging system methodical verification checks, CB750, CB550, CB500, CB400, and CB350.

Begin with problem verification and characterization with recorded data.
A -- Fully charge a known good battery.  Let it rest for 2 hours, off the charger, and measure the battery voltage.  (Target is 12.6-12.8V.)
B -- Start the bike and measure the battery voltage at idle, 2000, 3000, 4000, and 5000 rpm.
C -- Repeat the measurements of B with lighting off.

The above tests identify charging system success, failure, or degree of "faulty".  The success voltages are listed in the Shop manual.

D -- Assuming the above indicates faulty, do check the RECTIFIER diodes with a diode tester or ohmmeter capable of testing diodes and uses more than .7 volts to make the test(s).
Of the twelve test made in D, six must read low ohms and six must read very high ohms.

E- assuming no faults were found in D,  Measure the white and green wires disconnected from the REGULATOR.  CB750s should 6.8 ohms - ish,  CB550s/350s/ and 400s should read 4.9 ohms- ish.

F- If there are no bullet holes or road rash/divots on the alternator case, the stator is probably good.  But, you can check for yellow to yellow continuity (.35 ohms) among all the wires, and that no yellow wire has continuity to the engine case.

G- Assuming no faults found in D, E, and F, measure the disconnected terminals of the REGULATOR.  The black and white terminals should measure zero ohms (subtract meter error if there is any).  Higher than Zero ohms, indicates internal contact contamination needing cleaning and attention per shop manual.

H - Assuming D, E, F, and G have not found faults. We can verify all the of the charging system minus the regulator is functioning correctly, by using a temporary jumper to connect the disconnected white wire (normally attached to the REGULATOR) and connecting the White directly to the the battery POS terminal.  Repeat the B and C tests.  However, if at any time the battery voltage rises above 15V, stop the test.  Such an indication would prove the charging system capable of maintaining a known good battery.  If this test never achieves 15V, then there is a wire/connector issue in either the ground path leading back to the battery NEG terminal, a wiring/ connector issue withe the rectifier RED path to the battery POS terminal, or you made a mistake in D through G.

I - (not used, can be confused with L)

J -  The only parts that remain to prove or expose are the REGULATOR (in active mode) and the electrical path between the battery POS terminal and the black wire that connects to the REGULATOR.

K - Lying to and starving the regulator
The regulator can only do its job correctly if it gets a proper voltage report of true battery voltage status.  The Vreg monitors the Black wire for this status.  Measuring the voltage lost between the Battery terminals and the Vreg connections identifies problems that are not really the charging system's fault.
Two connection paths must be checked, the Battery POS terminal to the Black wire connection at the VReg, and the Battery NEG terminal to the Green wire connection to the Vreg.  A volt meter can measure these losses directly by placing a probe between the two identified points, Black path and then the green path.  The numbers are summed and the error seen by the Vreg quantified.  Anything over .5V loss is cause for concern and anything over 1V is a certain issue to be corrected.  Each connector, terminal, fuse clip, or switch in the pathway can cause voltage reporting loss.

The regulator also passes the received voltage on to to the Alternator field coil to create a magnetic field within the alternator,  The voltage level determines the strength of the magnetic field and the maximum output capability of the alternator.  Therefore, starving  the Vreg of true battery voltage leads to reduced max output capability of the alternator.

L - regulator operation/verification.
  The Vreg sends voltage to the alternator field in response to measured voltage which is battery state of charge.  Any voltage at the battery of less than 13.5V sends full black wire voltage to the alternator's white wire.  The alternator output will vary with RPM, even if "told" to produce max power by the Vreg.  If the alternator has enough RPM to overcome system load, any excess power is routed to the battery which will raise the battery voltage (slowly if depleted and rapidly if nearly full).   When the battery reaches 14.5V, the regulator reduces the voltage to the alternator, reducing output strength and preventing battery overcharge.  If the battery exceeds 14.7V, the regulator clamps the alternator field coil power to zero (0V), effective shutting off the alternator.

Because, there is electrical load from the system, an alternator that is not producing power allows the battery to deplete and the voltage falls.  The Vreg responds by turning the alternator back on in accordance with battery state/ charge level.

The Vreg state changes can be monitored/verified by observing the battery voltage state, and the White wire to the alternator field.  (Two meters are handy for this.)  The "trip" voltages can be adjusted with the adjust screw, while changing engine RPM and electrical load that the bike presents to the battery/charging system to "make" the battery reach the voltage levels need for the set trip points.  IE. with load reduced (lighting off) and the engine above 2500 RPM, a charged battery will attain 14.5 V.  Anything above that and the adjust screw needs to be backed out to keep the battery safe from harm.
The shop manual outlines bench set up mechanical adjustments that should be performed on unknown or tampered units.  These should be resolved before final trip point adjust tuning.

Note that while the system is working, the Vreg can change states rapidly before your very eyes., changing 5 times or more while you blink.  Therefore, you may have to mentally average values measured on the White wire if your selected meter doesn't do that for you.

Ok, starting the TwoTired charging test, but someone  may need to dumb things down for me.


A)
After full charge battery was sitting at 13.06V, admittedly I did not wait the 2 hours.

Key on and I drop to 12.8.  Kill switch set to on - 12.6

B) Started bike. At Idle I'm seeing 12.6.  I don't fully trust my tach, but the nice thing is it went from 12.6 at idle to 12.7 at the peak at very high RPMs.  Not sure where the chart is , but pretty sure I failed.

C) Same with the lights turned on. 12.6-12.7

D) Man it took me a minute to figure out where the rectifier was, and then decided I probably needed to take it off to test it. And then I was sticking the probes in the sides and trying to figure out which side of the diode I should have each lead on etc. Inconsistent results to say the least.

Then I think I wised up.  I have 3 yellow wires and 2 black going in.  As beat-up as this thing looks, I was getting the .5 from one black to each of the yellow then 0's when reversed.  The other black same reading but would get opposite(i.e. .5 when red on this one, where I got .5 with black on the other side).  Checking the two blacks against each other I got ~.9. But I don't think that means anything.


Z) - For some reason I thought I needed to peek at the Stator so I took that cover off with some diffifculty. Am I going to need to scrape and replace this gasket now?

Running to cook dinner but will add photos shortly .

But yeah assuming I am Now doing it right, it was not obvious to me at first that I didn't need to disassemble and was just checking wires at the plug connections
« Last Edit: August 11, 2025, 03:23:05 PM by turin39789 »

Offline turin39789

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having some trouble with photos, trying one at a time

Offline turin39789

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rectifier