Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Morala on December 10, 2024, 07:09:13 PM
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hope someone can help,i started the bike, 1974 550 today but when i pushed the starter button the starter kept turning over even when i turned the key off it just kept turning over until the battery ran down, never did this before so am at a loss as to what the cause could be any advice would be much appreciated cheers.
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Sounds like a stuck solenoid unit.
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I agree, duff solenoid
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The spring in the starter button can stick and the nylon type plastic can wear, resulting in the contact not breaking. I noticed a strange whirring noise when i was riding, starter was spinning while the engine was running and traced it to this.. Be very careful dismantling it, if you think that might be your issue. The spring and ball bearing like to fly off.
Edit: just thinking. This can't be the problem, as the starter would stop when the ignition is off. I don't see how your starter still spins with the ignition off, unless you have a short in the circuit, bypassing the ignition switch.
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I reckon the solenoid plunger and copper contact bar is sticking when engaged. It’s an easy fix.
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Just realised that this is a us 550 and in these the plastic contact assembly inside the rh switch can degrade and crack.
On these the button turns off the headlamp before making starter contact so it is possible that if the assembly breaks the starter contacts could be permanently contacting
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Should be easy enough to disconnect the small wires to the solenoid to identify if it's the power to the solenoid circuit causing the issue or if the solenoid itself has faulted.
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I’m not sure it can be the button mechanism as the owner has stated that killing the ignition didn’t stop the starter turning. I suspect it’s a mechanical problem with the solenoid plunger and copper contact bar.
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There is also some potential for collateral damage here. If the battery was healthy and continued to run the starter until fully discharged, not only may the battery be damaged, but the starter motor windings could also be damaged due to overheating.🥵
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Kill switch only stops coil circuit not the starter circuit
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I don’t quite understand that. You can start the bike with the ignition off?
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Kill switch only stops coil circuit not the starter circuit
Not the kill switch, he's turning it off with the ignition key switch.
Very odd you're getting constant power to the starter and it continues with the ignition switch off. Starter earth should be straight to the battery? So, to me, your problem is in the switched live. I can't think how you're getting a connection to battery positive down there that bypasses the ignition switch and the handlebars starter button. Do you have a stock wiring loom?
So difficult to trace remotely. Study your wiring diagram and trace how the starter gets power. Then it's a meter, to test the circuit. As you'll need the bike's battery connected, maybe disconnect the starter, to look after it and hook the terminal wires up to a bulb, maybe what you use to set points timing?
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The solenoid switch contacts posts are permanently live, being fed directly from the battery. The starting current is circa 110A. The ignition switch is fed directly from the fuse box and the fuse box is fed from the starter solenoid switch contact. Basically the entire electrical system is fed from battery, to solenoid contact post, to fuse box then to the ignition switch. The switched side of the ignition feeds the starter button and the coils. Basically, if you depress the starter button, the coil engages and although you may stop pressing the button, if the solenoid post within the solenoid jams in the closed position, it will continually run the starter regardless of the ignition position.
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I’ve just been in the garage to check. Turning the ignition off when depressing the starter stops the starter.
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Morala.
As a starter(pardon the pun), I recommend you remove and open the starter solenoid. Check to make sure the post moves freely and that the horizontal copper bar is not fused across the solenoid contact posts. If necessary you can flip the bar over to provide a nice set of fresh contacts.
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Morala.
As a starter(pardon the pun), I recommend you remove and open the starter solenoid. Check to make sure the post moves freely and that the horizontal copper bar is not fused across the solenoid contact posts. If necessary you can flip the bar over to provide a nice set of fresh contacts.
👍
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thanks for all your help,tried the bike today started without any problem so will leave it to see if the problem happens again,wont be using the bike over the winter so gives me time to keep an eye on it thanks again for all your advice.
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If the solenoid stuck once it will again so probably worth changing, they aint expensive
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Personally, I think that's a problem that needs sorting, not ignoring in the forlorn hope it will go away. For the relatively modest cost involved I would start by replacing the solenoid.
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You stated it went on to flatten the battery with the ignition off, that could end up as a damaged battery or a burnt out starter motor as collateral damage, plus a theoretical wiring loom issue caused by the current flow on earthed circuits
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TBH it’s a pretty quick job to split the solenoid and clean up the contacts. It’s probably a good investment in your time to avoid a potentially expensive collateral damage situation….just saying.
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cheers lads a new solenoid it is then
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Are you sure you can’t fix the existing one? They come apart really easily. The problem is probably the copper contact bar in the solenoid, which is readily accessible and easily cleaned up. Assuming of course it’s an original relay/solenoid.
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just an update on the solenoid problem, when i started to remove the solenoid i found one of the contact securing nuts was very loose could this be the problem, i have only got the bike so still learning the ins and outs of it cheers.
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I doubt it, if as you have stated the starter continued to crank over with the ignition off until the battery had run down, that could not be caused by a loose terminal.
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no problem, will replace solenoid and again thanks for all the advice
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It could have created arcing on the solenoid contacts within the unit causing the copper contact bar to temporarily fuse to the contact posts. 110A starting current and IsquaredR would create considerable heat. I’m not convinced a new solenoid would be required. I’d suggest opening the solenoid to check the internal contact bar before spending your money. Your choice of course.
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Can the solenoids be unscrewed Phil or is it some sort of crimping, can't say I've ever taken one to bits ?
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Bit of both on originals Ted
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My 1977 550 F2 original solenoid contacts canister and coil unit are joined together using two screws and a simple tongue and recess arrangement. I’ll try to get a picture tomorrow, as long as I don’t have to remove it to do so. Original units are very, very unsophisticated and all the better for it.
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another update, i removed the solenoid and cleaned all the contacts, checked the wiring refitted the unit, will keep an eye on it over the winter cheers for all your help again.
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Did you take it apart and clean the internal contacts?
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Hi Bryanj, yes i cleaned the contacts and checked the wiring then fitted the unit back in, hope everything works ok cheers.
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just an update re. ignition, after i cleaned the contacts and re fitted the unit it seems to be working ok but will keep an eye on it to be sure, again thanks for all your advice and help.