Hello,
In 1983 I bought an A10 plunger and restaured it completely.
But then I got married and had kids so the bike stayed in the garage for about 40 years.
It is still in good condition and functions, but the ammeter is wobbling.
The whole electrical system is original and the magdyno works, but I would like the ammeter to work correctly.
What could be the cause of the wobbling ?
The needle pivot may have dried out. You may find that it has an adjusterble pivot so you can take up the slack.
crude voltage regulation,
vibration from the road surface are just to name a few issues that can cause the needle to wobble.
Thanks for the advice.
I also read that it can be caused by a bad contact of the wiring.
Could it be the regulator ?
These ammeters are quite fragile and can show wild swinging readings and fail. They are suscepible to vibrations causing failure. If you look underneath, if it is genuine old Lucas instrument rather than one of the new repros you should see the head of a grub screw the other side of which is the pivot for the needle shaft. It may be sealed by some sort of mastic, careful adjustment of the grub screw may (or may not) stop wild fluctuations. You need to be very careful or you will lock the pivot.
The second photo show the later more robust type of ammeter introduced 1962/63. You can see the mastic sealing over the grub screw.
I would not assume the problem is due to the regulator, more likely the ammeter has had it.
Rectification is an assumption with a DC charging circuit. I have seen a waving needle with an alternator circuit and a change to a mosfet regulator which without planning to solved the waving needle issue.
Thanks for all the advice : I will see into it.