Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: RGP750 on May 10, 2023, 03:11:55 PM
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Hi All
I have a problem with my 72 500/4.Went out on it last year and everything perfect.
This year turn on ignition and dead short somewhere, frustrating nightmare.
Gradually disconnected areas of wiring, handlebar switches, rear light, horn regulator, etc and finally every connector in the headlight.
Thought it could be solenoid so replaced that, bypassed ignition switch , still doing it . any thoughts pleeeeeeeese!
Rich
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Difficult one to diagnose online.
So does it blow the fuse as soon as you switch the ignition on?
Have you done any work on the bike since you lay her up for the winter?
Is the regulator/ rectifier standard?
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I would start by disconnecting the red and white wires to the fuse box and rectifier and all the live feeds (anything with a black wire).
Reconnect the red and white wires one at a time and then the black wires one at a time until you find the problematic item section.
This will help to narrow it down.
You can also check the other side of the black wire connections for continuity to earth.
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Not done any work since last ride.
I have disconnected every wire I can think of and it still blows as soon as I turn the key, or cut out the switch and " hot wire-"
If I got to the situation when the fuse didn't blow I could start adding wires until it went again but not there yet.
What else can I disconnect?
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I had the same problem last year with my 500K1 Rich. Graham spent hours and hours trying to sort the problem, he checked and changed connectors and wires, he fitted new parts which may have been causing the issue, but still didn't find the problem. In the end I bought a new loom from Electrix World, he swapped the loom over and the problem was cured instantly and she's been tickity boo ever since. .
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Are you using the correct size fuse and not a car type 25 or 30A? If a large fuse has been fitted at any time, a wire may have fried internally in the loom itself and melted the insulation of one of the black wires. Only a single fuse on those bikes which makes diagnosis hard. If you have isolated all of the black wires (and also the black/white one if the kill switch is in the 'run' position), I can only think it's a loom problem.
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Brand new loom fitted last year when I gave it a tidy up .
Yes correct fuse fitted .
As I have said it ran perfectly last year and something has gone ary while standing .
Just don't know where to look now.
Nbefore getting silly and replacing everything again
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New loom? well I think we can discount that then, for the time being. It blows as soon as you turn the ignition switch? all black wires disconnected? You've hot wired it to isolate the ignition switch and it still blows? so not the ignition switch. I'd check the sub loom first Rich. It's one of the 500s major problems in that it only has one fuse, anything wrong and the whole bike dies, not a good idea. Check the wiring on the sub loom to see if any have shorted out. Disconnect every wire in the headlight first off. The reconnect systematically, do the indicators first, most of the problems seem to be caused by them in my experience.
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Have a good look at the loom under the tank by the coils, i have seen the loom melt there on the green wire if the main ground contact is not 100%
It melts inside the loom all the way along destroying other wires.
If thats ok first things i would disconnect are rectifier and regulator
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Good shout with the reg and rec Bryan, especially if Rich has had the side cover off, a lot trap wires putting it back on.
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Sounds like you have nearly disconnected everything on the main loom. If so do a continuity check between a black wire and a green wire. and if there is a short (other than the loom chafing on the frame somewhere) then it's the loom.
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Cheers guys
Already removed the regulator and andrectifier.
It really is looking at taking the loom off and seeing if I can find anything. Cheers all
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Brand new loom fitted last year when I gave it a tidy up .
Yes correct fuse fitted .
As I have said it ran perfectly last year and something has gone ary while standing .
Just don't know where to look now.
Nbefore getting silly and replacing everything again
Mine was originally a new aftermarket loom from DSS the year before Rich. Graham put another new loom on, changed the ignition switch and the sub loom. Never did find what part was at fault because i just wanted to ride her once she was running.
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Sounds silly but it sounds like you’ve got two wires connected that shouldn’t be, make sure when everything is back in place that all the connectors are separated as if it ran ok but doesn’t now has something moved and started touching? If it has you won’t find the fault. I’d plug it all back in and start one at a time again if you can as per suggested. I do think it sounds like a crap earth or a loom off job sadly
Sent from my iPhone using Tapatalk
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Nothing is left connected so my thoughts are melted loom for some reason. To me it's the only logical answer now. I'll try and get time in the next week to take it to bits I'll report back when I have done it .cheers all
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Firstly I am assuming that you did not disconnect the battery over winter & that as you describe it the bike was fine last year - nothing has changed as the bike has just stood unused - it just started to blow fuses when you turned the ignition on after the winter rest.
I'm racking my brains as to what could deteriorate as it has stood over the winter - it seems unlikely that a wire could chafe or that an alternator wire would somehow become disconnected and short as it has stood.
My only ever experiences of a similar type of problem was when a rectifier had rusted causing a short in the casing & when a regulator stuck - two separate episodes first one on a bike, the second on a car.
My suspicion is that if such a failure has blown a number of fuses it is likely that wiring in the loom has overheated leading to further dead short. I mention this as if something has caused the loom to fail replacing the loom could lead to another loom failure.
Not sure if it is possible that major internal battery cell failure could be a cause?
Might be worth checking the state/condition of the battery.
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Thanks for your thoughts. Battery off over winter on optimiser.
Motobatt , seems fine.
I took the loom off last night and externally looks fine I assume I have to unwrap it to check every wire.
That's the bit I can't get my head around , it was running fine
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Why unwrap it just use a multimeter and the wiring diagram.
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Thanks for your thoughts. Battery off over winter on optimiser.
Motobatt , seems fine.
I took the loom off last night and externally looks fine I assume I have to unwrap it to check every wire.
That's the bit I can't get my head around , it was running fine
Like I said in my previous reply, do a continuity check between any black wires and green. When you do that flex the loom at the same time with the meter still connected to see if there is continuity at anytime.
Failing that, you could sent it to that nice chap Ash on here..pretty sure he could check it out...sure he wouldn't mind :)
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Mottobbattt, you didntt by chance fit it backwards, i ask as i know the labeling is not the best
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Don't want to insult your skills but a few basics to check.
Normally the right hand side of the battery is the Negative terminal when fitted to the bike.
An earth lead goes from this Negative terminal to the engine.
The left side as you look at the battery is Positive and has a connection for the live side.
The battery on my 400 was fitted back to front when I bought the bike so both terminals were close to the frame. The earth lead had been attached to the rectifier mounting bolt.
My apologies in advance I do not want to offend anyone reading this post. I did wonder if any additional wires had been connected to the live side that might have been left off and caused a short circuit. My bike has an additional permanent fused cable on the live side connected to a special charging plug for my C-tek unit and to a volt meter I have fitted.
Just thinking of any possible reason why all that has changed is you have had the battery out over the winter and now it's faulting.
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Have you looked for any evidence of mice chewing a wire or 2? They are notorious for nesting in bikes over winter.
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Thanks Toko Jo I know Ash , I'll give him a call.
As for other suggestions. Yes battery is the right way around
The plug it in and one at a time theory is great if the fuse doesn't blow but as its still blowing it won't find it.
Still head scratching cheers
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If nothing is connected Rich except for the ignition switch (and you've tested that by isolating it) and the fuse is still blowing then it has to be a short in the loom. When I say nothing, I mean nothing at all anywhere on the bike, rear lights, points, coils etc.
In which case as Jo says, a simple test between black and green should show if it is the loom.
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That's tomorrow's plan. I just hope it shows up.7
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Thanks Toko Jo I know Ash , I'll give him a call.
As for other suggestions. Yes battery is the right way around
The plug it in and one at a time theory is great if the fuse doesn't blow but as its still blowing it won't find it.
Still head scratching cheers
Replacing the fuse with a lightbulb makes fault finding much easier (and cheaper, doesn't cost so many fuses.)
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I am baffled as to how the fault has developed Rich - I for one will be very interested as to the cause of problem when you identify it. Iirc it was a new loom as well.🤔
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I am baffled as to how the fault has developed Rich - I for one will be very interested as to the cause of problem when you identify it. Iirc it was a new loom as well.🤔
All wiring is capacity, doesn't melt under designed for load. And insulation, to prevent leaking into something else. Well that's the simplified way I look at it.
So, either overloaded with excess or too small to handle the task reasonably. Or, damaged physically, the insulation, to be insufficient in stopping leaking to give overload.
Checking any multi plugs first to make sure there's no obvious breach to catch you out is worthwhile.
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I noticed Nigel that the 550F sub loom I bought to replace my old one used thinner red wire from the starter solenoid down the the multi blade connector than the original Honda one, that wire on the Honda one is slightly thicker than the rest, due no doubt to the fact it carries the entire load of the bike, the replacement used the same gauge of wire as the rest. Not a good idea. I intend to replace that wire even though it's brand new.
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Some considerable number of years ago I looked at a Ford car for someone with some curios problems.
The throttle cable and clutch cable had both melted their outside plastic covers ! Slow and difficult starting too, he'd left the earth strap off to the engine block after working on it, using starter had then tracked down those two routes in scavenging earth supply to crank it :)
Damned leaky stuff yer electrick-tricity ;D it'll get out with any slight chance offered.
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Up date.
Well I took everything off I could find including the battery.
Did the continuity green?black test on the loom and couldn't find anything. Put loom back on and
fuse NOT BLOWING ,put together rear light wiring , tested , Ok switches OK horn ok everything else all ok .
A eureka moment fuse still ok . Now here is the next problem , what the hell is wrong now. Nothing works :-\
no horn, starter, dash lights rear light Nothing. What the hell have I missed. HELLLLP!!!!!
Done Battery test and 12v
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Are your fuses okay? I had a problem on my 550 where everything died, turned out the fuse looked intact but had just degraded with age and was open circuit.
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Hi Steve
Please see the start of the thread cheers
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Can you measure volts coming out of the fuse now, en route into the loom ?
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what meter between fuse and red wire going to ignition switch?
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Yes, to check if anything is now going into loom.
Positive lead to fuse exit, negative lead to battery -
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OK Back track.
Just found out why nothing working, knew it would be something stupid OOPs! multi plug on the loom not plugged in :-[
But now I have plugged it in Fuse has blown so where to look now.
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Looking more like it'll need unwrapping to understand it.
If there's nothing obvious, and it still blows the fuse when nothing is connected (any devices) to influence the outcome, then it must have some compromise inside.
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if it didn't blow before I connected the multiple in the side panel would that not mean the problem in in whatever the socket is connected to ?
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That suggests the main loom is a problem as the fuse is not connected till that big block is connected due to being part of the sub loom.
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Thanks Brian just done this this morning.
Disconnect block, check black live into headlight for continuity and all is fine , plug block in and it shorts.
I then check black in sub loom and ok, check black on regulator ok. Something is happening when it is plugged in .????¿
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Have you tried it with just the rectifier plug disconnect & the flasher unit not connected?
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Don't want to rejoice just yet but it looks like the whole mess is down to a faulty Indicator relay.
I have ordered a new one and will report back.
Looks like Ted may get first prize.
Watch this space
Cheers all for your thoughts.
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The flasher unit on my old 400 was this inside after standing for over 10 years.
.(https://live.staticflickr.com/65535/51917764175_d0a5d5d5a0_o.jpg) (https://flic.kr/p/2n6N7v6)flasher unit (https://flic.kr/p/2n6N7v6) by Macabe Thiele (https://www.flickr.com/photos/187487200@N03/), on Flickr
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think that's shot. mine was a repro only fitted 2 years ago. >:(
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So was yours 2 or 3 terminal ?
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3 terminal Ted
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Not as easy to find the 3 terminal ones they are the earthed type.
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Hopefully you've found the culprit Rich, does it all function with that relay removed in the interim ?
If so, well spotted Ted :)
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Yes everything fine, plug in relay and pop.
hope the new one works ok. I would have liked an original but can't find one.
Cheers Rich
yes well done Ted, I owe you one.
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New conundrum
New flasher relay fitted , fuse didn't blow,
Eureka.
Next problem the lights
Don't flash :'( any thoughts please.
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As in the flasher button on the left hand switch doesn't flash the headlight Rich?
First thing to check if so, is the blue wire actually connected in the headlight?
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Sorry not sure what you mean.
Headlight is fine main and dip. . I don't have a headlight flash button .
Right indicator turns front and rear indicators but not flashing and left is the same .
I have tried another different unit and it's the same ?????
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You should have said indicators don’t flash Rich not lights don’t flash.
Sounds like a bad earth, have you tried running a wire from the indicators to a good earth point?
A UK CB500 should have a headlight flasher Rich, is it an import?
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Sorry just thought as I was talking about relay.
All 4 indicators are earthed , I'll try another new earth thanks .
Not an import it's a k1 from Steve admin.
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Is the replacement relay just one with two terminals?
If it is you may need to reverse the connections as one way the flashing circuit does not operate.
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3 terminal as previous one.
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3 terminal as previous one.
Are you using conventional Tungsten bulbs of the correct wattage or LED's?
Is it an electronic flasher unit that works at a fixed rate irrespective of the bulb load?
Are the terminals marked differently - I suspect it might just back to front on the flashing circuit - leave the earth circuit as it is & try switching the terminals - for safety you can add a bulb type circuit test to remove any chance of blowing the flasher unit?
It will not flash if its a standard flasher unit with LED bulbs or if the bulb wattage is too low - sometimes you get a hyper fast flashing rate instead.
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All the bulbs are as they were before the flasher unit started blowing the fuse. Obviously tracked the relay down as the culprit. and bought
a new relay (well 2 actually both different makes) .I have tried reversing the black and grey and same result with both relays.
God I hate electrics
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This might sound basic but are you sure the flasher units are the correct ones for your total bulb wattage & designed for a negative earthed vehicle?
When I replaced the flasher unit in my 400 I could not find the ones with three terminals so fitted a two terminal unit.
I am thinking that you might have the later car type flasher unit they will be marked with an earth designed for modern cars that are positive earth.
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Relays are usually marked with paint blobs next to the terminals so you get them right.(well Honda ones are) Yours sounds like it's a power problem, the grey wire seems to be working as it should but the black wire doesn't. Try removing the black wire and testing it for voltage, or run a wire from the battery to the black terminal on the relay and see if that works, if so then it's a black wire problem, could be a dirty connection or a broken wire. If not the black do the same with the grey.
Electrics are easy, I kinda like doing them, it's just having a logical approach and persevering. It's when it goes internal on generators etc that I lose interest. Wiring though, I quite like.
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Try connecting the two wires at the relay together with a jumper and see if the bulbs light up when switch moved, if so problem is flasher relay, if not wiring is faulty
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Am I correct in assuming that when you move the indicator switch to say the left position that both left bulbs illuminate but do not flash on & off?
If so I think it must be related to your flasher relay.
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Thanks Brian I'll give that a try tomorrow.
Ted I have used 2 relays , both new and different makes with the same result.
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Thanks Brian I'll give that a try tomorrow.
Ted I have used 2 relays , both new and different makes with the same result.
Yes but are they the correct part you have fitted?
As someone here has posted earlier if you bridge those two wires (not the earth) can you make them flash on and off by breaking and making the connection the connection? If it's yes you know where the answer lies. I'm not great with electrics and have no idea how a two terminal flasher really works but it does.
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Thanks Brian I'll give that a try tomorrow.
Ted I have used 2 relays , both new and different makes with the same result.
Yes but are they the correct part you have fitted?
As someone here has posted earlier if you bridge those two wires (not the earth) can you make them flash on and off by breaking and making the connection? If it's yes you know where the answer lies. I'm not great with electrics and have no idea how a two terminal flasher really works but it does.
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Well at last all is well.
I gave up on the 2 flasher units I bought, one on eBay and one from a local motor factors, (Lucas for M/C)
got a NOS Honda one from a mate , all is well going for a ride later.
Thanks for all of your input.
Rich
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Would be useful to know the part number if you have it for future reference Rich my relay has been replaced with a two connector type that does not fit the (broken) rectangular suspension rubber.
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38300-323-009 Ted. Rubber mount, round type is 38306-323-000
There is an alternative used in the US market, where we got a round relay they got a oblong or square one, rubber mount is then square, 38306-107-670 and the square relay, 2 pin version is now 38301-KJ6-741/2/3