Stuttering with lights on - Charging problem?

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Stuttering with lights on - Charging problem?

Post by Mick D »

Hi Christian

Don't lose heart, it's best to find out what's wrong with your system even if you decide to modify to 12V,

Basic, (very ;) ), alternator checks:

Check the coils for short to ground - set the multi-meter to continuity test, ( beeps when probes touched together), place one probe to ground / battery positive and the other onto each of the three output leads from the alternator in turn. The multimeter should not beep, if it does you have a short from the alternator and the stator will need to be repaired.

Resistance check of the alternator coils - set the multi-meter to resistance / Ohms, connect one probe to the green/white alternator wire and the other to each of the other wires in turn. You should see a reading from both wires and neither should be zero. If one is zero that group of coils is open circuit and the stator will require repair.

If the tests above don't indicate the stator needs repair the chances are your alternator is good.

Let us know how you get on and we can suggest the next step.

Regards Mick
OEW591
Posts: 158
Joined: Mon Jan 01, 1990 12:00 am
Location: CAMBRIDGESHIRE UK

Re: Stuttering with lights on - Charging problem?

Post by OEW591 »

Hi Christian,

AMOC Parts Service does sell to members outside of the UK. Currently there is a minimum order level of £135.00 to EU countries as a result of Brexit. You would also need to pay shipping costs and Customs Duty and VAT on the arrival of the goods in Germany. Have a look on the spares website and see if we have the parts you need and if we do you will need to decide if the purchase is cost-effective for you.

Regards

Alan (New Guy at Kettering)
schrottschlecker
Posts: 46
Joined: Tue Nov 14, 2017 8:36 am
Location: GERMANY

Re: Stuttering with lights on - Charging problem?

Post by schrottschlecker »

Dear all,

thanks for your advice so far. I am victim of the flooding and currently need to take care of other stuff.
One day I will check the alternator and get the AJS going, although I might shy away from British bikes due to the Brexit situation :(

Cheers,
Christian
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dave16mct
Member
Posts: 3234
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Stuttering with lights on - Charging problem?

Post by dave16mct »

Sorry to hear that Christian. Was your house flooded?
Dave.
schrottschlecker
Posts: 46
Joined: Tue Nov 14, 2017 8:36 am
Location: GERMANY

Re: Stuttering with lights on - Charging problem?

Post by schrottschlecker »

dave16mct wrote: Sat Jul 24, 2021 4:42 pm Sorry to hear that Christian. Was your house flooded?
Dave.
Yes, unfortunately. Grandmother's appartment and all her stuff 1,10 meter under water. My bike in the garage below drown for 3 days, 1200km after total restoration :cry:
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dave16mct
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Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Stuttering with lights on - Charging problem?

Post by dave16mct »

That's a very sad sight. I hope your family are all safe.
Dave.
jmbradford
Member
Posts: 24
Joined: Mon Jan 01, 1990 12:00 am
Location: MIDDLESEX UK

Re: Stuttering with lights on - Charging problem?

Post by jmbradford »

Christian
If you bike is original with a seperate switch for ignition and one for lights then the charging system may appear simple but is quite complex and clever because the lighting switch also changes the wiring of the alternator to compensate.
One mistake that can be made is to leave the ignition switch in emergency mode , the bike starts but will not run properly at speed , emergency mode changes the alternator wiring to provide power pulses for the ignition for starting but the pulses are not correctly timed when running at speed and the bike normally starts missfiring.
The alternator has 2 sets of windings , high power and low power with a common wire connected to both coils. The alternator can be tested by disconnecting all wires and connecting a 12v 60W headlamp bulb across all wires in turn with the bike running at fast tickover , brightest light is between low and high windings as the coils are in series , the other wire is the common.
If the alternator is fine (connect alternator back up) then remove the neg wire from the rectifire (not the bolt one) and connect your 12v 60W lamp between chassis and the neg terminal of the rectifire , the lamp will get brighter with sidelights then headlight. The lighting/ignition switching shorts one alternator winding with the lights off , removes this short with sidelights and then connects both windings together with headlights on , the charging is thus controlled quite well.
If all is not well a common problem can be the plugs on the switches (if you have them) or corrosion and worn contacts inside the switches , the switches have to handle quite alot of current with a 6v system . I have had to replace them due to intermittent contacts , if you are brave then you can unpeen the switch body and clean the contacts , beware of springs and things in side the switch , go steady.
Hope this explination helps you and others too.
John B.
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