Rough running

[DavidZ1R]

Hi guys,I'm lost with this one, new plugs, electronic ignition, which has been swapped, carbs off twice and cleaned through, with cleaner and compressed air, standard patten coils, which I have swapped, trouble is, starts ok and ticks over fine, air screws adjusted 1 1/4 turns out, plugs look sooty, needles set on centre grove, but it runs rough at low speed up to 40mph, open it up and flies no trouble, z1000a1, standard air box, when i laid it up last autumn it ran fine, got it out in spring, rough? Any suggestions before I sell it as parts

[Kev1R]

If you haven't checked already:
Might be worth looking at - fuel tank tap / gauze filter or blocked tank vent.
You could change the fuel anyway.
HT leads or connections - try spare set of plug caps if you have any.
If working ok last year it sounds like something has degraded - sods law says it's always the last thing on the list that you check.

[Ultim8pc]

Based on my experiences I wrote an article which you may find useful:
https://airevalleyclassics.co.uk/badrunning.html

[DavidZ1R]

Well, I hope I have got to the bottom of it, read your post Nigel, very interesting, after a good long ponder, considering I had checked everything else, I checked voltage at battery at tick over, shows 11.5v, no lights on or anything, rev to 4000 rpm, shows 11.8 h 12v, replaced combined regulator/rec unit with the original one, same, checked stator, all yellow wires show ground, so I am hoping that's the problem. Unless you know different.

[Gray17]

Ok well first of all your battery should show over 12v even if not charging so chances are if you havn't had it on a smart charger through the winter theres a good chance batteries had it, not sure if youre aware but most batteries loose about 1.2v per month even if not connected so need topping up regularly. You can try putting a large load 65w bulb or similar on it and watch voltage on a multimeter it should hold at + 12v. Next you could try charging it using a smart charger overnight, these can restore batteries but not always depends how discharged its is and how long it was left that way and also batt type AGM, Gel or lead acid. Well worth a try.
Next def something wrong with charging system with engine running you should get 14v even with lights on it should be over 13.6v. Your 3 yellows do go to ground but should show a resistance not dead short, depends on model, if you download a workshop manual should tell you what readings in ohms to expect. Also check the magnets too as they do tend to loose magnetism over time, this will also effect your charge voltage if any.
Also use a decent multimeter as cheap ones arnt that accurate but will give yoy an indication.
Check your voltage at each coil again should be battery voltage ie 12v+ yours being low to start with will def cause issues., also check all connections for shorts and corrosion in case thats pulling voltage down
Hope that helps

[DavidZ1R]

The battery was fully charged up a few weeks back, it spins the engine ok and fires up ok, the voltage does bounce around ABIT on tick over, up and down. And yes, + probe on yellow wires, - probe on the engine, shows ground with no resistance on all three wires. According to the book it's a fail on stator.

[Gray17]

If youre starting the bike on battery alone with the coils also drawing current the battery will run down so voltage get lower and lower without the alternator to top it up and will probably be the cause of your rough running.
I would start by removing the alternator loom away from the bike and check it's entirety for damage or shorts and the connector too as can melt, if ok pay particular attention to where it enters the caseing, theres a rubber grommet that goes hard and can crack, if all ok you will have to strip the alternator down and replace the coils, its very unusual for all 3 to coils to go faulty together when not used but not unheard of. If its the alternator loom at fault you can buy replacements but need soldering on. You can also get the coils too not the easiest of things to fit though!

[Ultim8pc]

Well, I hope I have got to the bottom of it, read your post Nigel, very interesting, after a good long ponder, considering I had checked everything else, I checked voltage at battery at tick over, shows 11.5v, no lights on or anything, rev to 4000 rpm, shows 11.8 h 12v, replaced combined regulator/rec unit with the original one, same, checked stator, all yellow wires show ground, so I am hoping that's the problem. Unless you know different.

You should be getting at least 13v at tickover and up to 14.5v at 4k RPM with a known good reg/rec, battery and no wiring issues.
Likely your stator is weak an not outputting the correct AC voltage or frequency. Off the top of my head I think you should see 50VAC accross any two yellows when running. (Need to test each yellow against the other two).

[DavidZ1R]

Well back to square one, I went through the stator checks, now all seems ok, getting ac voltage coming out on all 3 yellows, when I connect everything up, no more than 12v at the battery, if I disconnect the feed wire from the rectifier and test, shows over 13v at tick over, and rises with throttle, all good, plug the wire into the fuse/battery feed, same drop, so it can only be the fusebox, unlikely, or the battery not accepting the charge, which i cannot believe, any help before i lose the will to live.

[moizeau]

What voltage does the battery show when just connected to a mains charger? If it is lead acid battery with the removable caps each cell can be tested independently with a voltmeter to see if you've got a dead or dying cell. You could also use a car / mower battery with jump leads to see what voltage is reaching that battery (with the bike battery disconnected).

[DavidZ1R]

I'm taking out the battery tomorrow for a full bench charge, also Im going to put a new centre loom on, the one with 4 coloured sockets, the original is still on, might be a little corrosion in there, can but try.

[Gray17]

Not sure if youre sorted as yet but from what youve described sounds to me like either a faulty battery or youve got a short somewhere pulling voltage down. I would check all connectors and joints and also loom esp under tank area for possible shorts look for damage to sheaving due to schaffing or heat, also check inside headlamp bowl too. Not easy finding intermittent or unforseen loom damage but it has to be 1 or the other.
Goid luck.

[Ultim8pc]

Not sure if youre sorted as yet but from what youve described sounds to me like either a faulty battery or youve got a short somewhere pulling voltage down. I would check all connectors and joints and also loom esp under tank area for possible shorts look for damage to sheaving due to schaffing or heat, also check inside headlamp bowl too. Not easy finding intermittent or unforseen loom damage but it has to be 1 or the other.
Goid luck.

I would agree.

[DavidZ1R]

New battery due today, will report back when I've fitted it.

[DavidZ1R]

I spoke with Big Fluff, Will on Sunday, he said a bad battery rejects charge, must admit I was surprised, anyway, put a new battery on, charging good now, just a sodding battery.