CB550 F2 Misbehaving...

[Steph550]

Hi all,

After being very well behaved for a long time, my 550 F2 has decided to start misbehaving! Basically, the bike has started cutting out at random moments while I'm riding. It seems to happen mainly when I've ridden somewhere, stopped for a cup of tea, then ride off again when the bike has cooled down a fair amount (say after being parked for half an hour). Up until just now, it only seemed to be happening when I let the throttle off completely, but it's just happened while cruising at 70mph on a dual carriageway so that's thrown that theory out the window! There's no warning at all, no coughing, just a sudden complete cut out. The bike also sometimes takes a while to start again afterwards so may be fuel related? Electrics all still work at the time of the cutout.

Has anyone experienced similar symptoms at all, or have any ideas what may be causing it? I replaced the fuel filter and checked the fuel tap last year, so I doubt that's the problem, although I won't rule it out.

Or maybe the 550 is just jealous that I've got a second bike!

Any ideas would be appreciated!

Steph.

[mickwinf]

if it cut out suddenly at 70 I would suspect electrical problem. maybe a short on the cut out circuit?

[tom400f]

+1

You would have to suspect electrics if it's either on or off and nothing in between. Kill switch or anything in the low-tension side of the ignition, may be the wiring from your points is earthing (though that may only affect 2 cyls at once of course)

[LesterPiglet]

I had the same problem. Faulty ignition switch.

[Bryanj]

Check the connector block on the bottom of the ignition switch as the harness is tightly run and they can work loose.

It is possible to buy just the contacts part of the switch so you don't have to have another key if that is what you would like. I did have a couple of NOS bases ----IF I CAN FIND THEM---

[hairygit]

+1 with Lester on ignution switch, my 750F1 did the same several times, I used to wiggle the ingitionn switch while still rolling in gear and it wiuld run fine again until the next major bump in the road. It turned out one of the plastic lugs holding the switch to the lock had snapped off, so fitted a new switch, problem solved

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[Steph550]

Sorry if I'm being stupid (electrics aren't my strong point!) but looking at the wiring diagram, if it was a problem with the ignition switch would other things not also stop working? When the engine cuts the neutral light and oil light still work, as does everything else.

This also doesn't seem to be related to bumps in the road.

I'll have a look at the kill switch circuit and ignition switch today and see if I can find an obvious problem.

Cheers,

Steph.

[Bryanj]

Not necessarily Steph, trouble with electrics is you cant see or smell it but by christ it hurts when it bites!!

[LesterPiglet]

Jiggle the wires behind the ignition while the bike is running and see if it reacts but you saying the neutral light is still on when it cuts out makes me think it isn't the switch.

[florence]

I've had this, loose barrel in the ignition switch, wiggle the key and it cuts out.  It once happened to me in the dark, luckily not going round a bend, extremely distressing!  I replaced the switch with a Honda item and before long, same problem.  I now have a landrover ignition switch, seems fine.  If it happens again I shall dispense with ignition switch altogether in favour of a simple toggle like I had on my BSA.

[Steph550]

Had the bike out this morning, fired it up and wiggled the key, the ignition switch, the connector, and the wires around the ignition switch. The bike just sat there happily ticking over.. Ignition switch barrel/connector definitely not loose. Took the bike out for a ride, behaved beautifully. Parked up for lunch, then on the way back she cut out, halfway round a roundabout!

  I suspect it may be something in the engine cutout circuit?

Steph

[Bryanj]

Try the fuses and the connections at the ends

[Lobo]

Steph.. if fuses not the answer try feeding (ie hot wiring) the two +ve feeds to the coils (black/white) directly to the battery +ve & then take it out for a spin. Ie, In this way deleting the ignition switch AND handlebar kill-switch out of the circuit. If the bike OK then you've narrowed it down to ignition switch (which you already doubt) OR handlebar loom / kill switch.

You'll obviously want to leave the bike standing for a while to simulate the problem... do disconnect the coils during this time to avoid burning them out. (& indeed anytime the engine not running)

If the bike still misbehaves check the earthing of the points backplate is sound.(a long shot, I know)

If the bike now 'good' have a careful check of handlebar loom wiring - ie feed / return to kill switch connections. Kill switch, as mentioned by Tom, likely the culprit... often you can 'clean' a switch by exercising it on/off a dozen plus times. Not ideal... but can work. Perhaps spray a squirt of switch cleaner in there... tho' again not ideal versus a strip down & clean.

Cheers, & hoping ya don't have to strip the handlebars..
Simon.

[Steph550]

Thanks Bryan, have had a look at the fuses and they and all their connections look absolutely fine.

Simon, thanks very much for the advice. I've just tracked down the feeds and return wires to the kill switch and cleaned the connectors. They didn't seem too bad but a couple of the bullet connectors were slightly loose so have made sure they're all nice and secure, and cleaned them up. We'll see if that makes a difference! If not I'll try your suggestion of 'hot wiring' the coils.

Thanks for your help! I notice you're in Hampshire by the way Simon, which general area? If you're towards the New Forest area and see a broken down 550 at the side of the road, chances are it'll be me! 

Cheers,

Steph.

[Bryanj]

If they are the glass tube fuses its a good idea to take them out and pull gently on the ends as the element inside can come loose on the end cap