AJS 31 battery charging issues

[aobp11]

Hello Geoff,

Perhaps I should say nothing since I don't have an alternator bike and no power box ... but blood is ticker than water.
The 3.1 A , later 2.3 A, discharge is large I think for a 12 V system. It's determined by the replacement ignition coils(s) used in the modification. The power box will also drain a low current for its electronic circuits. The drop will be due to heating and increase of copper wire resistance in the coil(s). But this issue is unrelated to the charging problem.

I suppose the power box output voltage (15 V) was with normally connected output? You gave this voltage in 2 decimals, 15.19 V. Does that mean that this voltage is rather independent of revs? If so, this might indicate that the power box is regulating it's output voltage to the maximum that is (internally) set for the situation of an unloaded output (or rather low current output). The AC input current can still be very high (your 10 A) when the power box regulates the output voltage by periodically shorting its input.
So your findings could simply (and hopefully) be explained by a bad or interrupted connection between the box output and the rest of the circuit. Probably the box output is connected straightforward to an ignition switch terminal.
You can measure AC and DC current with the amp-clamp. So could you also measure the (average) DC output current of the power box? That would give a more trustworthy test for charging system performance. Some digital multimeters give misleading readings in the presence of switching devices and iginition circuits. You might also try a head light bulb between box output and earth. Check that it's normally burning when ignition is on but the engine not running. At increased revs it should get brighter but not much brighter than when connected across the battery.

Albert

[Geoff Sharpe]

Geoff,

Off at a bit of a tangent, looking at your picture there should be a plain clutch plate surface under the clutch pressure plate, depending on the clutch type/year this will either be a bonded one side or completely plain plate.

Thanks for that Duncan. Sorting the clutch was going to be my next target once I've solved the electrical issue. It's useful and interesting that you've spotted something odd about it. I've always thought the clutch lever was unusually heavy but don't really know how it should feel. I wondered whether people had much stronger hands back in the sixties. Do you think the feel of it could be due to what you have spotted?


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[Duncan]

Geoff

When you investigate you may find you need another plate which could add to the overall pressure on the plates, usually though (apart from spring tension) the cable is the cause of a heavy clutch, either the route of it, lubrication (don't oil nylon lined ones) or the pull of the lifting lever could be off square.

[Geoff Sharpe]

Geoff

When you investigate you may find you need another plate which could add to the overall pressure on the plates, usually though (apart from spring tension) the cable is the cause of a heavy clutch, either the route of it, lubrication (don't oil nylon lined ones) or the pull of the lifting lever could be off square.

Thanks for your advice Duncan. I'll let you know how I get on in due course.


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[Geoff Sharpe]

Hi Geoff,
Afraid I can't be much help other than saying with my recent issues I found that with ignition on, engine not running, you can expect to see around a 2amp discharge when CB points are closed and zero discharge when they are open.

Have you tried turning engine over slowly to open CB points and observe the above?

These numbers are from my 6 volt G3 so will prob be different for your 12 volt system.

Good luck

Steve

Hi Steve,
Thanks for that, very interesting.
I'm not at home now for the next couple of days so can't check, but I'm pretty sure the 2.5 Amp discharge is constant when cranked over slowly. The bike is so eager to start since my work on it that it's not an easy test to do. Perhaps I need to take the plugs out?


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Hi Steve,
yesterday I took the fuel tank off, removed spark plugs but connected them back to the ignition leads and let them rest on the engine cooling fins, so making electrical contact. I could then crank the engine over slowly and just watch the ammeter. With the battery fully charged it was showing a 4 amp discharge when I turned the ignition on Sure enough, as on your bike, the current drawn dropped to zero when it was cranked to the position that coincided with points open. So that current must be drawn by the ignition coil, presumably normal behaviour.
Maybe the alternator just isn't working hard enough to offset the discharge.


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[dave16mct]

I presume you've checked the basics? Have you disconnected the alternator and checked each wire for leakage between it and earth? Have you put your meter on the did-connected leads with the engine running ( or as we used to do use a big headlamp bulb, don't rev up or it'll blow!)Have you got a good clean earthing point? If you're on positive earth the leads from the powerbox should be black to ammeter (-), red to earth (+) the two yellow leads go to the alternator (either way 'round)
Alternator- have you got the spacer between the sprocket and rotor? Check the measurements, depending on the make etc you may have the rotor mis-aligned with the stator. For max power it need to be centred on it. New alternators aren't necessarily the same as the originals, but we use the original spacers! Have you ckecked the air gap? Should be about 12thou.Wind about 3 turns of plastic insulation tape on the rotor and refit the case. See what happens. You may find it hasn't touched at all in which case you might have the old 6 volt rotor with a big airgap. Also remove the rotor and try it for magnetism. If a spanner will lift it ,it's ok to use .if not you may need a new one. Phew!
Cheers Dave.

[Expat]

Hi Steve,
yesterday I took the fuel tank off, removed spark plugs but connected them back to the ignition leads and let them rest on the engine cooling fins, so making electrical contact. I could then crank the engine over slowly and just watch the ammeter. With the battery fully charged it was showing a 4 amp discharge when I turned the ignition on Sure enough, as on your bike, the current drawn dropped to zero when it was cranked to the position that coincided with points open. So that current must be drawn by the ignition coil, presumably normal behaviour.
Maybe the alternator just isn't working hard enough to offset the discharge.


Geoff,

After much testing and a lot of help and advice here, I too have come to the conclusion that it's just old and with some small losses in the circuitry, just not up to charging enough. For my purposes, it is adequate with regular use of the battery tender.

Good luck as you continue to investigate though. Do keep us up to date with progress.

Cheers. Steve.

[Geoff Sharpe]

I presume you've checked the basics? Have you disconnected the alternator and checked each wire for leakage between it and earth? Have you put your meter on the did-connected leads with the engine running ( or as we used to do use a big headlamp bulb, don't rev up or it'll blow!)Have you got a good clean earthing point? If you're on positive earth the leads from the powerbox should be black to ammeter (-), red to earth (+) the two yellow leads go to the alternator (either way 'round)
Alternator- have you got the spacer between the sprocket and rotor? Check the measurements, depending on the make etc you may have the rotor mis-aligned with the stator. For max power it need to be centred on it. New alternators aren't necessarily the same as the originals, but we use the original spacers! Have you ckecked the air gap? Should be about 12thou.Wind about 3 turns of plastic insulation tape on the rotor and refit the case. See what happens. You may find it hasn't touched at all in which case you might have the old 6 volt rotor with a big airgap. Also remove the rotor and try it for magnetism. If a spanner will lift it ,it's ok to use .if not you may need a new one. Phew!
Cheers Dave.

Hi Dave, it's been a couple of weeks since you took the trouble to write all the helpful advice above. Thanks very much for that. I'm back on the trail now, albeit a bit sporadic with other aspects of life getting in the way.
I've been trying to check out all the items you've listed. The air gap is spot on 12 thou. The stator and rotor are misaligned by about 3.5mm. I can easily deal with that by packing the stator inboard. While I've got it dismantled I definitely want to check out the rotor magnetisation but I'm having trouble getting the nut undone. I'm following guidance given in an AJS handbook, engage top gear, press down on brake, etc. I'm getting nowhere. Is it a right hand thread? I haven't tried heat on it yet. Any other tips or advice please would be a help.
The general state of the rotor doesn't look great, see attached photo. I'd like to understand the significance of the shield shape with the cross in it. My guess is that it's for timing setup. I'd love to be put right and educated on that by anyone out there who can help.

Image1475146710.680757.jpg

[SPRIDDLER]

I definitely want to check out the rotor magnetisation but I'm having trouble getting the nut undone.......I haven't tried heat on it yet. Any other tips or advice please would be a help.

Careful with heat, Geoff!!

When heated above 176° Fahrenheit (80° Celsius), magnets will quickly lose their magnetic properties. The magnet will become permanently demagnetized if exposed to these temperatures for a certain length of time or heated at a significantly higher temperature

[Mick D]

Hi

The nut is a normal thread, anti-clockwise to loosen. Yours has been locked by the three centre pop marks you can see in the photo.

Have you tried shock loads rather than just spanner pressure? Either lock the transmission as you suggest, high gear and footbrake, or sprag it by wedging a piece of wood or soft metal between the clutch sprocket and chain, or secure the clutch using a tool made from two clutch plates secured together. Then place a suitable spanner on the nut and hit it firmly with a heavy hammer, it should move after one or two thumps.

If you have access to a pneumatic socket wrench, (wheel gun), this will also work, probably without the need for any further securing of the drive train.

Regards Mick