The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: bikerbob on 22.06. 2019 17:03

Title: Dynamo burnt out
Post by: bikerbob on 22.06. 2019 17:03
Went out on the A7 yesterday everything OK for about 25 miles the with the headlight on it suddenly showed a discharge equivalent to having the headlight on and no engine running when I got home  checked and dynamo only putting out 1.5 volts.  Stripped the dynamo today very strong smell of burning. armature burnt out insulation between the segments next to the field coils melted and smeared over the inside of the dynamo also bits of armature wire inside of dynamo. Will have to order new armature and may as well oder new field coil as do not know if the heat may have affected it.  Will have ride the A65 till I get it all fixed again. Is there a running clearance between the field coil and the  armature if so what is it, does not look as though the field coil has been touching the armature but maybe I should check on reassmbley.
Title: Re: Dynamo burnt out
Post by: chaterlea25 on 22.06. 2019 19:54
Hi Bob,
This should probably get moved to the correct section of the forum

What wattage headlamp bulb is fitted?
are you running 6 or 12v ?
A bad battery or regulator can also contribute to a burned out dyno

Title: Re: Dynamo burnt out
Post by: Swarfcut on 23.06. 2019 07:42
Bobby, What a stroke of good luck...Failure on the longest day, and the old machine still got you home.

 Now you have a chance to upgrade to a 12 volt Dynamo with not much greater cost than a standard unit. OK, you will have to add the cost of the voltage control unit, but to my mind 12 volts is well worth having.


 Bobby, What a stroke of bad luck, after all  the money you spent on that new dynamo, loom, electronic ignition  etc you are let down by the vagaries of an inadequate design, poorly produced in some far away establishment.

 Your choice mate, delete either/or/both as appropriate!

Title: Re: Dynamo burnt out
Post by: bikerbob on 23.06. 2019 09:03
The bike is all original 6 volt the only non original parts on the bike are a DVR2 regulator an in line oil filter in the tol box and it now has an original Avon handlebar fairing fitted it was rewired about 3 years ago because the original wiring was past it's best. It does not have electronic ignition my other bike a A65 has a pazon electronic system fitted. The dynamo itself was completely overhauled  about 4 years ago. The battery is a cyclon battery which is OK.  Here is a photo of both bikes taken before the fairing was fitted to the A7 also the A65 as bought.

Title: Re: Dynamo burnt out
Post by: Black Sheep on 23.06. 2019 10:08
A bit odd. The only time that happened to me was when I was running a standard E3L dynamo on the A10 with a 12 volt regulator and battery. Could the regulator have had something to do with it? In my case, I gave up on the 12 volts and stuck to a 6 volt setup and it has been fine ever since.
However, my A7 has a 12 volt dynamo (both field coil and armature changed) and has been running happily for some years now.
I would have the regulator checked.