AJS & Matchless Owners Club

Hi, I've just noticed that for the1st time in over a year my bike will only start and run in the E mode setting.
The battery is charged and the lights all operate ok, but will only start and run when the switch is in the emergency position, if I then try to switch it back to the I setting after a few mins running it immediately cuts out. I've not changed or touched anything. Any thoughts ?

Is the battery knackered or is it definately holding charge?

It's about 6 years old,I'm not sure of the condition , when on charge it seems to get up around 6.9 / 7.1 volts , but I haven't got means to a load test on it

I am getting a spark at the plug in both I & E switch setting

But it could be a weak spark in I mode. When you charge the battery what is the reading on your multimeter after 24 hours, 48 hrs. Still around 7 volts?

Dubbsy wrote: ↑Thu Aug 24, 2023 2:37 pm It's 6 years old.......

6 years is a pretty long time. If it's a wet lead-acid type and you've run it flat a couple of times or left it in a discharged state for a week or three it probably needs replacing.

haven't got means to a load test on it

You could do a load test by turning the bike headlight on. If it's duff the light will die after say, 5 to 10 minutes, (depending upon the capacity of the battery and the wattage of the headlamp bulb).
As Spooky implied, the residual open circuit voltage immediately after or within an hour or two after charging is no indication of its condition.

Thanks all, I've taken the battery off and put it on charge, I'll report back findings in a couple of days . Agree it looks like a duff battery....

Well, the battery showed 6volts, however I put it on a slow trickle charge for a week to get it up to the max of 7.2v and let it stabilise for a few days. Put on the bike and started 1st time on the standard Ignition setting ! So it seems the battery just didn't have enough amperage to keep it running but would do in the E mode. I'll keep a check on it, but suspect the battery has seen better days.

Good to know she's going again!

In E mode the battery isn't actually in play, you're just getting a pulse of unrectified alternating current from one section of the alternator to the ignition coil as you kick her over, to provide the spark.
The fact that she started in E tells us the alternator coil(s) that generates that pulse works a treat. So that's a Tick.

What worried me though was that at the beginning of the thread here you said the battery could provide lights etc OK - but that the machine wouldn't start except in E. The current needed for the lights far exceeds that needed to create a spark . . . so I was bemused and confused as to 'why?' It seemed to me that something other than just the battery might be playing up, because once running the alternator should support things even if the battery is at its last gasp.

I'm sort-of wondering whether the engine will stay running in the normal Ign position if you disconnect the battery? Normally, a standard battery / coil set-up ought to.
Also, is the battery is still being charged as it should be / was being in the past, showing a decent 7+v across the terminals with the engine running at moderate rpm, with the ammeter sending only good tidings?

If all continues well, that'll be great. But if there's a weak link in these things, it's often the rectifier (which is luckily cheap as chips).

Thanks, that sounds all logical, I'll start her up again tomorrow and do those checks & report back