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SOHC.co.uk Forums => CB350/400 => Topic started by: Athame57 on October 26, 2022, 02:05:23 PM

Title: Sudden engine cut outs
Post by: Athame57 on October 26, 2022, 02:05:23 PM
About four times in a couple of weeks now I've been riding along and engine stops. I coast to a near stop, go into neutral and hit start button engine fires up again. Fuel starvation I would rule out and probably electrical as well (?) any ideas?
Title: Re: Sudden engine cut outs
Post by: SteveW on October 26, 2022, 02:22:14 PM
Check the fuses, mine did this.
Fuses looked intact but when you removed  them from the fuse holder the ends just fell off.
Title: Re: Sudden engine cut outs
Post by: Laverdaroo on October 26, 2022, 02:48:52 PM
About four times in a couple of weeks now I've been riding along and engine stops. I coast to a near stop, go into neutral and hit start button engine fires up again. Fuel starvation I would rule out and probably electrical as well (?) any ideas?

Well it's one or the other!

I'd start with fuses and check all the connectors attributed to the ignition circuit and clean before putting back together. Make sure everythings connected and making contact. Either that or the neutral switch, side stand switch if it has one or the clutch switch, again, if it has one. That would be where I would look first.
Even if you have it ticking over and wiggle everything and try to reproduce the fault, simple fix and cheapest way to start for me.
Title: Re: Sudden engine cut outs
Post by: Nurse Julie on October 26, 2022, 03:01:07 PM
Definitely check the fuse George. The metal caps can vibrate and come loose, so they still have contact but not all the time.
Title: Re: Sudden engine cut outs
Post by: Bryanj on October 26, 2022, 03:10:49 PM
My guess is ignition switch or connector too it
Title: Re: Sudden engine cut outs
Post by: McCabe-Thiele (Ted) on October 26, 2022, 03:56:10 PM
Have you replaced the fuse box? - my DS aftermarket one failed when fitted -wires not soldered on properly at the back on the ignition circuit.
Title: Re: Sudden engine cut outs
Post by: SteveW on October 26, 2022, 03:57:12 PM
Dodgy kill switch?
Title: Re: Sudden engine cut outs
Post by: Athame57 on October 26, 2022, 04:47:06 PM
I've checked a few things like my battery leads and fuses, I couldn't really find anything wrong but I changed some fuses anyway. I did find a few snails taking refuge under my panels though..... I'm not sure what to think of that!  :o
Title: Re: Sudden engine cut outs
Post by: McCabe-Thiele (Ted) on October 26, 2022, 05:17:50 PM
I've checked a few things like my battery leads and fuses, I couldn't really find anything wrong but I changed some fuses anyway. I did find a few snails taking refuge under my panels though..... I'm not sure what to think of that!  :o

No ring of Table Salt around your bike for snail protection!
Title: Re: Sudden engine cut outs
Post by: Cappodimonte on October 26, 2022, 07:37:28 PM
Sudden stop failure points to electrical issue not fuel, that’s usually a stutter or misfire. Best to start with battery and it’s connections especially the earth strap to the frame, it could be as simple as it has loosened a little and/or rusted at the frame.
Title: Re: Sudden engine cut outs
Post by: Oddjob on October 26, 2022, 07:47:56 PM
Need more info, does the engine stops but the lights etc stay on? Just an engine stop could mean the kill switch contacts, full shut down is most likely an ignition switch fault
Title: Re: Sudden engine cut outs
Post by: Cappodimonte on October 26, 2022, 09:33:25 PM
Just a thought but, how long has the battery been on the bike ? Is it an old lead/acid or new gel type
If it’s been in situ for a fair while and is lead/acid it could be a battery plate has part failed and vibration causes a separation, short and immediate stop. The other fail points are kill switch or ignition switch, check ALL connections however and clean them up, electricity can build up resistance at rusted or corroded connection points
If it’s a gel battery then get it professionally checked out, anything electrical can fail anytime, these things can really wind you up.
Title: Re: Sudden engine cut outs
Post by: Athame57 on November 02, 2022, 05:00:56 PM
Just a thought but, how long has the battery been on the bike ? Is it an old lead/acid or new gel type
I put the current battery in four years ago, it looks alright but I've never had a bike so long as this, I'll change it. I see on DSS the battery they offer for the CB400F is a gel type now, anyone experienced this offering of theirs yet? Now and then the starter button doesn't respond, usually first push of the day, by moving the kill switch and pressing....then putting it back and pressing it works again. I've opened it up but can't see anything wrong as meets the eye though. Maybe try some WD40?
Title: Re: Sudden engine cut outs
Post by: Laverdaroo on November 02, 2022, 05:08:19 PM
Sounds like thats the culprit. Clean it towithin an inch if its life and re test then move down the wires. Cheap and easy.
Title: Re: Sudden engine cut outs
Post by: 400 Cafe Racer on November 02, 2022, 06:03:12 PM
Just a thought but, how long has the battery been on the bike ? Is it an old lead/acid or new gel type
I put the current battery in four years ago, it looks alright but I've never had a bike so long as this, I'll change it. I see on DSS the battery they offer for the CB400F is a gel type now, anyone experienced this offering of theirs yet? Now and then the starter button doesn't respond, usually first push of the day, by moving the kill switch and pressing....then putting it back and pressing it works again. I've opened it up but can't see anything wrong as meets the eye though. Maybe try some WD40?

Failing all else, as a belt and braces solution, you could wire a "Secret Hidden " bye pass switch, concealed from view. Wired direct from the battery - through its own seperate fuse - and connected to the ignition switch output wire.  This would enable you to get home without being stranded.  If the Ignition switch or fuse or anything on the live side fails you would be covered. :)

Dennis
Title: Re: Sudden engine cut outs
Post by: Lobo on November 02, 2022, 09:37:15 PM
Given both the Kill Switch and the Start button are failing it might just be the multi-connector - can’t remember if it’s found within the headlamp or boot below the tank?

Do the headlamp / park lamp behave 100% as these too share the same multi connector?

Have a look at this wiring diagram, and note the three black (ie switched live) feeds all originate from a common multi-connector.
Title: Re: Sudden engine cut outs
Post by: Athame57 on November 03, 2022, 07:20:48 AM
Given both the Kill Switch and the Start button are failing it might just be the multi-connector
My kill switch works fine... I'll still go have a look at the multi-connector though.  ;)
Title: Re: Sudden engine cut outs
Post by: Lobo on November 03, 2022, 11:59:38 AM
Sorry - misunderstood the bit about starter button / kill switch.

I guess the easiest way to check is to have the engine running whilst moving the under tank connections boot up & down a bit in the hopes of a cut-out. (or within the headlamp bowl wherever…)
Title: Re: Sudden engine cut outs
Post by: Oddjob on November 03, 2022, 02:49:30 PM
Won't be a block connector if the wires go through the bars, it will be multiple individual connectors. However the black connector could still be the common factor.
Title: Re: Sudden engine cut outs
Post by: TrickyMicky on November 03, 2022, 11:55:49 PM
I had a problem with the main beam warning and indicator warning lights on the handlebar display. It turned out to be where all the earth wires joined inside the headlamp. 40-odd year old bullet connectors were quire heavily tarnished meaning that the earth current tracked through whatever route possible. Our bikes might be old, but at least we can access all the individual wires and connections, and with a little patience they clean up quite well.  The other similar problem I had, which caused a lot of head scratching, was the main fuse failing quite often. It turned out to be the multi connector behind the fuse carrier, upon unplugging it all the connections inside it were a nice green colour!! Apparently if a fuse "blows" in the middle of the glass then it's a short circuit, but in my case the end caps of the fuse were falling off through overheating, caused by current having difficulty being drawn through the poor connection. 30 minutes work with a set of jewellers' files cured it. Be lucky. Mike.
Title: Re: Sudden engine cut outs
Post by: McCabe-Thiele (Ted) on November 04, 2022, 05:38:25 AM
For removing green contact corrosion I followed Julie's tip & used Cillit Bang Limescale remover. A squirt on the stuff on the contacts then a few minutes later it just came off revealing shiny brass spade terminals. Even used on the voltage regulator spades.

Updated: I used an old toothbrush afterwards & rinsed with WD40.
Title: Re: Sudden engine cut outs
Post by: Athame57 on November 05, 2022, 01:53:49 AM
For removing green contact corrosion I followed Julie's tip & used Cillit Bang Limescale remover. A squirt on the stuff on the contacts then a few minutes later it just came off revealing shiny brass spade terminals.
At that price I'll order some anyway!  :D
Title: Re: Sudden engine cut outs
Post by: Cappodimonte on November 10, 2022, 07:55:32 AM
Have sorted your cut out problem yet or are you still working on it ?, having re read the topic it could be so small as to be a ‘Dry joint’ where wires are soldered to a switchgear of motherboard, it would initially work but electrical resistance builds up and bingo stoppage. It’s a bit like a skybox that goes static, you turn it off, wait ten seconds and switch on, hey presto it works again. Think I’d have another look at the internals of the kill switch, after all the bits are 40+ years old.
Title: Re: Sudden engine cut outs
Post by: Athame57 on November 19, 2022, 10:19:04 PM
Have sorted your cut out problem yet or are you still working on it ?
I got a new battery from DSS, a mainenance free gel one. Easier starting now and no cut outs on the move. There remains an issue of the starter button sometimes failing to work unless I give it a go with the kill switch on, then back to normal. I opened the unit but can't see anything obvious.
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